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