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
make_uml_dir(void)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 */
remove_files_and_dir(char * dir)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 */
is_umdir_used(char * dir)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 */
umdir_take_if_dead(char * dir)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
create_pid_file(void)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
set_umid(char * name)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
make_umid(void)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
make_umid_init(void)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
umid_file_name(char * name,char * buf,int len)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
get_umid(void)346 char *get_umid(void)
347 {
348 return umid;
349 }
350
set_uml_dir(char * name,int * add)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
remove_umid_dir(void)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