xref: /qemu/os-posix.c (revision 27a4a30e) 
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 #include "qemu-common.h"
33 /* Needed early for CONFIG_BSD etc. */
34 #include "net/slirp.h"
35 #include "qemu-options.h"
36 #include "qemu/error-report.h"
37 #include "qemu/log.h"
38 #include "sysemu/runstate.h"
39 #include "qemu/cutils.h"
40 
41 #ifdef CONFIG_LINUX
42 #include <sys/prctl.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 /*
84  * Find a likely location for support files using the location of the binary.
85  * When running from the build tree this will be "$bindir/../pc-bios".
86  * Otherwise, this is CONFIG_QEMU_DATADIR.
87  */
88 char *os_find_datadir(void)
89 {
90     g_autofree char *exec_dir = NULL;
91     g_autofree char *dir = NULL;
92 
93     exec_dir = qemu_get_exec_dir();
94     g_return_val_if_fail(exec_dir != NULL, NULL);
95 
96     dir = g_build_filename(exec_dir, "..", "pc-bios", NULL);
97     if (g_file_test(dir, G_FILE_TEST_IS_DIR)) {
98         return g_steal_pointer(&dir);
99     }
100 
101     return g_strdup(CONFIG_QEMU_DATADIR);
102 }
103 
104 void os_set_proc_name(const char *s)
105 {
106 #if defined(PR_SET_NAME)
107     char name[16];
108     if (!s)
109         return;
110     pstrcpy(name, sizeof(name), s);
111     /* Could rewrite argv[0] too, but that's a bit more complicated.
112        This simple way is enough for `top'. */
113     if (prctl(PR_SET_NAME, name)) {
114         error_report("unable to change process name: %s", strerror(errno));
115         exit(1);
116     }
117 #else
118     error_report("Change of process name not supported by your OS");
119     exit(1);
120 #endif
121 }
122 
123 
124 static bool os_parse_runas_uid_gid(const char *optarg)
125 {
126     unsigned long lv;
127     const char *ep;
128     uid_t got_uid;
129     gid_t got_gid;
130     int rc;
131 
132     rc = qemu_strtoul(optarg, &ep, 0, &lv);
133     got_uid = lv; /* overflow here is ID in C99 */
134     if (rc || *ep != ':' || got_uid != lv || got_uid == (uid_t)-1) {
135         return false;
136     }
137 
138     rc = qemu_strtoul(ep + 1, 0, 0, &lv);
139     got_gid = lv; /* overflow here is ID in C99 */
140     if (rc || got_gid != lv || got_gid == (gid_t)-1) {
141         return false;
142     }
143 
144     user_pwd = NULL;
145     user_uid = got_uid;
146     user_gid = got_gid;
147     return true;
148 }
149 
150 /*
151  * Parse OS specific command line options.
152  * return 0 if option handled, -1 otherwise
153  */
154 int os_parse_cmd_args(int index, const char *optarg)
155 {
156     switch (index) {
157     case QEMU_OPTION_runas:
158         user_pwd = getpwnam(optarg);
159         if (user_pwd) {
160             user_uid = -1;
161             user_gid = -1;
162         } else if (!os_parse_runas_uid_gid(optarg)) {
163             error_report("User \"%s\" doesn't exist"
164                          " (and is not <uid>:<gid>)",
165                          optarg);
166             exit(1);
167         }
168         break;
169     case QEMU_OPTION_chroot:
170         chroot_dir = optarg;
171         break;
172     case QEMU_OPTION_daemonize:
173         daemonize = 1;
174         break;
175 #if defined(CONFIG_LINUX)
176     case QEMU_OPTION_enablefips:
177         fips_set_state(true);
178         break;
179 #endif
180     default:
181         return -1;
182     }
183 
184     return 0;
185 }
186 
187 static void change_process_uid(void)
188 {
189     assert((user_uid == (uid_t)-1) || user_pwd == NULL);
190     assert((user_uid == (uid_t)-1) ==
191            (user_gid == (gid_t)-1));
192 
193     if (user_pwd || user_uid != (uid_t)-1) {
194         gid_t intended_gid = user_pwd ? user_pwd->pw_gid : user_gid;
195         uid_t intended_uid = user_pwd ? user_pwd->pw_uid : user_uid;
196         if (setgid(intended_gid) < 0) {
197             error_report("Failed to setgid(%d)", intended_gid);
198             exit(1);
199         }
200         if (user_pwd) {
201             if (initgroups(user_pwd->pw_name, user_pwd->pw_gid) < 0) {
202                 error_report("Failed to initgroups(\"%s\", %d)",
203                         user_pwd->pw_name, user_pwd->pw_gid);
204                 exit(1);
205             }
206         } else {
207             if (setgroups(1, &user_gid) < 0) {
208                 error_report("Failed to setgroups(1, [%d])",
209                         user_gid);
210                 exit(1);
211             }
212         }
213         if (setuid(intended_uid) < 0) {
214             error_report("Failed to setuid(%d)", intended_uid);
215             exit(1);
216         }
217         if (setuid(0) != -1) {
218             error_report("Dropping privileges failed");
219             exit(1);
220         }
221     }
222 }
223 
224 static void change_root(void)
225 {
226     if (chroot_dir) {
227         if (chroot(chroot_dir) < 0) {
228             error_report("chroot failed");
229             exit(1);
230         }
231         if (chdir("/")) {
232             error_report("not able to chdir to /: %s", strerror(errno));
233             exit(1);
234         }
235     }
236 
237 }
238 
239 void os_daemonize(void)
240 {
241     if (daemonize) {
242         pid_t pid;
243         int fds[2];
244 
245         if (pipe(fds) == -1) {
246             exit(1);
247         }
248 
249         pid = fork();
250         if (pid > 0) {
251             uint8_t status;
252             ssize_t len;
253 
254             close(fds[1]);
255 
256             do {
257                 len = read(fds[0], &status, 1);
258             } while (len < 0 && errno == EINTR);
259 
260             /* only exit successfully if our child actually wrote
261              * a one-byte zero to our pipe, upon successful init */
262             exit(len == 1 && status == 0 ? 0 : 1);
263 
264         } else if (pid < 0) {
265             exit(1);
266         }
267 
268         close(fds[0]);
269         daemon_pipe = fds[1];
270         qemu_set_cloexec(daemon_pipe);
271 
272         setsid();
273 
274         pid = fork();
275         if (pid > 0) {
276             exit(0);
277         } else if (pid < 0) {
278             exit(1);
279         }
280         umask(027);
281 
282         signal(SIGTSTP, SIG_IGN);
283         signal(SIGTTOU, SIG_IGN);
284         signal(SIGTTIN, SIG_IGN);
285     }
286 }
287 
288 void os_setup_post(void)
289 {
290     int fd = 0;
291 
292     if (daemonize) {
293         if (chdir("/")) {
294             error_report("not able to chdir to /: %s", strerror(errno));
295             exit(1);
296         }
297         TFR(fd = qemu_open("/dev/null", O_RDWR));
298         if (fd == -1) {
299             exit(1);
300         }
301     }
302 
303     change_root();
304     change_process_uid();
305 
306     if (daemonize) {
307         uint8_t status = 0;
308         ssize_t len;
309 
310         dup2(fd, 0);
311         dup2(fd, 1);
312         /* In case -D is given do not redirect stderr to /dev/null */
313         if (!qemu_logfile) {
314             dup2(fd, 2);
315         }
316 
317         close(fd);
318 
319         do {
320             len = write(daemon_pipe, &status, 1);
321         } while (len < 0 && errno == EINTR);
322         if (len != 1) {
323             exit(1);
324         }
325     }
326 }
327 
328 void os_set_line_buffering(void)
329 {
330     setvbuf(stdout, NULL, _IOLBF, 0);
331 }
332 
333 bool is_daemonized(void)
334 {
335     return daemonize;
336 }
337 
338 int os_mlock(void)
339 {
340     int ret = 0;
341 
342     ret = mlockall(MCL_CURRENT | MCL_FUTURE);
343     if (ret < 0) {
344         error_report("mlockall: %s", strerror(errno));
345     }
346 
347     return ret;
348 }
349