xref: /openbmc/qemu/os-posix.c (revision e0091133)
1 /*
2  * os-posix.c
3  *
4  * Copyright (c) 2003-2008 Fabrice Bellard
5  * Copyright (c) 2010 Red Hat, Inc.
6  *
7  * Permission is hereby granted, free of charge, to any person obtaining a copy
8  * of this software and associated documentation files (the "Software"), to deal
9  * in the Software without restriction, including without limitation the rights
10  * to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
11  * copies of the Software, and to permit persons to whom the Software is
12  * furnished to do so, subject to the following conditions:
13  *
14  * The above copyright notice and this permission notice shall be included in
15  * all copies or substantial portions of the Software.
16  *
17  * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
18  * IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
19  * FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL
20  * THE AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
21  * LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
22  * OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN
23  * THE SOFTWARE.
24  */
25 
26 #include "qemu/osdep.h"
27 #include <sys/wait.h>
28 #include <pwd.h>
29 #include <grp.h>
30 #include <libgen.h>
31 
32 /* Needed early for CONFIG_BSD etc. */
33 #include "net/slirp.h"
34 #include "qemu/qemu-options.h"
35 #include "qemu/error-report.h"
36 #include "qemu/log.h"
37 #include "sysemu/runstate.h"
38 #include "qemu/cutils.h"
39 
40 #ifdef CONFIG_LINUX
41 #include <sys/prctl.h>
42 #include "qemu/async-teardown.h"
43 #endif
44 
45 /*
46  * Must set all three of these at once.
47  * Legal combinations are              unset   by name   by uid
48  */
49 static struct passwd *user_pwd;    /*   NULL   non-NULL   NULL   */
50 static uid_t user_uid = (uid_t)-1; /*   -1      -1        >=0    */
51 static gid_t user_gid = (gid_t)-1; /*   -1      -1        >=0    */
52 
53 static const char *chroot_dir;
54 static int daemonize;
55 static int daemon_pipe;
56 
57 void os_setup_early_signal_handling(void)
58 {
59     struct sigaction act;
60     sigfillset(&act.sa_mask);
61     act.sa_flags = 0;
62     act.sa_handler = SIG_IGN;
63     sigaction(SIGPIPE, &act, NULL);
64 }
65 
66 static void termsig_handler(int signal, siginfo_t *info, void *c)
67 {
68     qemu_system_killed(info->si_signo, info->si_pid);
69 }
70 
71 void os_setup_signal_handling(void)
72 {
73     struct sigaction act;
74 
75     memset(&act, 0, sizeof(act));
76     act.sa_sigaction = termsig_handler;
77     act.sa_flags = SA_SIGINFO;
78     sigaction(SIGINT,  &act, NULL);
79     sigaction(SIGHUP,  &act, NULL);
80     sigaction(SIGTERM, &act, NULL);
81 }
82 
83 void os_set_proc_name(const char *s)
84 {
85 #if defined(PR_SET_NAME)
86     char name[16];
87     if (!s)
88         return;
89     pstrcpy(name, sizeof(name), s);
90     /* Could rewrite argv[0] too, but that's a bit more complicated.
91        This simple way is enough for `top'. */
92     if (prctl(PR_SET_NAME, name)) {
93         error_report("unable to change process name: %s", strerror(errno));
94         exit(1);
95     }
96 #else
97     error_report("Change of process name not supported by your OS");
98     exit(1);
99 #endif
100 }
101 
102 
103 static bool os_parse_runas_uid_gid(const char *optarg)
104 {
105     unsigned long lv;
106     const char *ep;
107     uid_t got_uid;
108     gid_t got_gid;
109     int rc;
110 
111     rc = qemu_strtoul(optarg, &ep, 0, &lv);
112     got_uid = lv; /* overflow here is ID in C99 */
113     if (rc || *ep != ':' || got_uid != lv || got_uid == (uid_t)-1) {
114         return false;
115     }
116 
117     rc = qemu_strtoul(ep + 1, 0, 0, &lv);
118     got_gid = lv; /* overflow here is ID in C99 */
119     if (rc || got_gid != lv || got_gid == (gid_t)-1) {
120         return false;
121     }
122 
123     user_pwd = NULL;
124     user_uid = got_uid;
125     user_gid = got_gid;
126     return true;
127 }
128 
129 /*
130  * Parse OS specific command line options.
131  * return 0 if option handled, -1 otherwise
132  */
133 int os_parse_cmd_args(int index, const char *optarg)
134 {
135     switch (index) {
136     case QEMU_OPTION_runas:
137         user_pwd = getpwnam(optarg);
138         if (user_pwd) {
139             user_uid = -1;
140             user_gid = -1;
141         } else if (!os_parse_runas_uid_gid(optarg)) {
142             error_report("User \"%s\" doesn't exist"
143                          " (and is not <uid>:<gid>)",
144                          optarg);
145             exit(1);
146         }
147         break;
148     case QEMU_OPTION_chroot:
149         chroot_dir = optarg;
150         break;
151     case QEMU_OPTION_daemonize:
152         daemonize = 1;
153         break;
154 #if defined(CONFIG_LINUX)
155     case QEMU_OPTION_asyncteardown:
156         init_async_teardown();
157         break;
158 #endif
159     default:
160         return -1;
161     }
162 
163     return 0;
164 }
165 
166 static void change_process_uid(void)
167 {
168     assert((user_uid == (uid_t)-1) || user_pwd == NULL);
169     assert((user_uid == (uid_t)-1) ==
170            (user_gid == (gid_t)-1));
171 
172     if (user_pwd || user_uid != (uid_t)-1) {
173         gid_t intended_gid = user_pwd ? user_pwd->pw_gid : user_gid;
174         uid_t intended_uid = user_pwd ? user_pwd->pw_uid : user_uid;
175         if (setgid(intended_gid) < 0) {
176             error_report("Failed to setgid(%d)", intended_gid);
177             exit(1);
178         }
179         if (user_pwd) {
180             if (initgroups(user_pwd->pw_name, user_pwd->pw_gid) < 0) {
181                 error_report("Failed to initgroups(\"%s\", %d)",
182                         user_pwd->pw_name, user_pwd->pw_gid);
183                 exit(1);
184             }
185         } else {
186             if (setgroups(1, &user_gid) < 0) {
187                 error_report("Failed to setgroups(1, [%d])",
188                         user_gid);
189                 exit(1);
190             }
191         }
192         if (setuid(intended_uid) < 0) {
193             error_report("Failed to setuid(%d)", intended_uid);
194             exit(1);
195         }
196         if (setuid(0) != -1) {
197             error_report("Dropping privileges failed");
198             exit(1);
199         }
200     }
201 }
202 
203 static void change_root(void)
204 {
205     if (chroot_dir) {
206         if (chroot(chroot_dir) < 0) {
207             error_report("chroot failed");
208             exit(1);
209         }
210         if (chdir("/")) {
211             error_report("not able to chdir to /: %s", strerror(errno));
212             exit(1);
213         }
214     }
215 
216 }
217 
218 void os_daemonize(void)
219 {
220     if (daemonize) {
221         pid_t pid;
222         int fds[2];
223 
224         if (!g_unix_open_pipe(fds, FD_CLOEXEC, NULL)) {
225             exit(1);
226         }
227 
228         pid = fork();
229         if (pid > 0) {
230             uint8_t status;
231             ssize_t len;
232 
233             close(fds[1]);
234 
235             do {
236                 len = read(fds[0], &status, 1);
237             } while (len < 0 && errno == EINTR);
238 
239             /* only exit successfully if our child actually wrote
240              * a one-byte zero to our pipe, upon successful init */
241             exit(len == 1 && status == 0 ? 0 : 1);
242 
243         } else if (pid < 0) {
244             exit(1);
245         }
246 
247         close(fds[0]);
248         daemon_pipe = fds[1];
249 
250         setsid();
251 
252         pid = fork();
253         if (pid > 0) {
254             exit(0);
255         } else if (pid < 0) {
256             exit(1);
257         }
258         umask(027);
259 
260         signal(SIGTSTP, SIG_IGN);
261         signal(SIGTTOU, SIG_IGN);
262         signal(SIGTTIN, SIG_IGN);
263     }
264 }
265 
266 void os_setup_post(void)
267 {
268     int fd = 0;
269 
270     if (daemonize) {
271         if (chdir("/")) {
272             error_report("not able to chdir to /: %s", strerror(errno));
273             exit(1);
274         }
275         TFR(fd = qemu_open_old("/dev/null", O_RDWR));
276         if (fd == -1) {
277             exit(1);
278         }
279     }
280 
281     change_root();
282     change_process_uid();
283 
284     if (daemonize) {
285         uint8_t status = 0;
286         ssize_t len;
287 
288         dup2(fd, 0);
289         dup2(fd, 1);
290         /* In case -D is given do not redirect stderr to /dev/null */
291         if (!qemu_log_enabled()) {
292             dup2(fd, 2);
293         }
294 
295         close(fd);
296 
297         do {
298             len = write(daemon_pipe, &status, 1);
299         } while (len < 0 && errno == EINTR);
300         if (len != 1) {
301             exit(1);
302         }
303     }
304 }
305 
306 void os_set_line_buffering(void)
307 {
308     setvbuf(stdout, NULL, _IOLBF, 0);
309 }
310 
311 bool is_daemonized(void)
312 {
313     return daemonize;
314 }
315 
316 int os_set_daemonize(bool d)
317 {
318     daemonize = d;
319     return 0;
320 }
321 
322 int os_mlock(void)
323 {
324 #ifdef HAVE_MLOCKALL
325     int ret = 0;
326 
327     ret = mlockall(MCL_CURRENT | MCL_FUTURE);
328     if (ret < 0) {
329         error_report("mlockall: %s", strerror(errno));
330     }
331 
332     return ret;
333 #else
334     return -ENOSYS;
335 #endif
336 }
337