xref: /qemu/os-posix.c (revision 2f28d2ff) 
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 <unistd.h>
27 #include <fcntl.h>
28 #include <signal.h>
29 #include <sys/types.h>
30 #include <sys/wait.h>
31 /*needed for MAP_POPULATE before including qemu-options.h */
32 #include <sys/mman.h>
33 #include <pwd.h>
34 #include <grp.h>
35 #include <libgen.h>
36 
37 /* Needed early for CONFIG_BSD etc. */
38 #include "config-host.h"
39 #include "sysemu.h"
40 #include "net/slirp.h"
41 #include "qemu-options.h"
42 
43 #ifdef CONFIG_LINUX
44 #include <sys/prctl.h>
45 #endif
46 
47 static struct passwd *user_pwd;
48 static const char *chroot_dir;
49 static int daemonize;
50 static int fds[2];
51 
52 void os_setup_early_signal_handling(void)
53 {
54     struct sigaction act;
55     sigfillset(&act.sa_mask);
56     act.sa_flags = 0;
57     act.sa_handler = SIG_IGN;
58     sigaction(SIGPIPE, &act, NULL);
59 }
60 
61 static void termsig_handler(int signal, siginfo_t *info, void *c)
62 {
63     qemu_system_killed(info->si_signo, info->si_pid);
64 }
65 
66 void os_setup_signal_handling(void)
67 {
68     struct sigaction act;
69 
70     memset(&act, 0, sizeof(act));
71     act.sa_sigaction = termsig_handler;
72     act.sa_flags = SA_SIGINFO;
73     sigaction(SIGINT,  &act, NULL);
74     sigaction(SIGHUP,  &act, NULL);
75     sigaction(SIGTERM, &act, NULL);
76 }
77 
78 /* Find a likely location for support files using the location of the binary.
79    For installed binaries this will be "$bindir/../share/qemu".  When
80    running from the build tree this will be "$bindir/../pc-bios".  */
81 #define SHARE_SUFFIX "/share/qemu"
82 #define BUILD_SUFFIX "/pc-bios"
83 char *os_find_datadir(const char *argv0)
84 {
85     char *dir;
86     char *p = NULL;
87     char *res;
88     char buf[PATH_MAX];
89     size_t max_len;
90 
91 #if defined(__linux__)
92     {
93         int len;
94         len = readlink("/proc/self/exe", buf, sizeof(buf) - 1);
95         if (len > 0) {
96             buf[len] = 0;
97             p = buf;
98         }
99     }
100 #elif defined(__FreeBSD__)
101     {
102         static int mib[4] = {CTL_KERN, KERN_PROC, KERN_PROC_PATHNAME, -1};
103         size_t len = sizeof(buf) - 1;
104 
105         *buf = '\0';
106         if (!sysctl(mib, ARRAY_SIZE(mib), buf, &len, NULL, 0) &&
107             *buf) {
108             buf[sizeof(buf) - 1] = '\0';
109             p = buf;
110         }
111     }
112 #endif
113     /* If we don't have any way of figuring out the actual executable
114        location then try argv[0].  */
115     if (!p) {
116         p = realpath(argv0, buf);
117         if (!p) {
118             return NULL;
119         }
120     }
121     dir = dirname(p);
122     dir = dirname(dir);
123 
124     max_len = strlen(dir) +
125         MAX(strlen(SHARE_SUFFIX), strlen(BUILD_SUFFIX)) + 1;
126     res = g_malloc0(max_len);
127     snprintf(res, max_len, "%s%s", dir, SHARE_SUFFIX);
128     if (access(res, R_OK)) {
129         snprintf(res, max_len, "%s%s", dir, BUILD_SUFFIX);
130         if (access(res, R_OK)) {
131             g_free(res);
132             res = NULL;
133         }
134     }
135 
136     return res;
137 }
138 #undef SHARE_SUFFIX
139 #undef BUILD_SUFFIX
140 
141 void os_set_proc_name(const char *s)
142 {
143 #if defined(PR_SET_NAME)
144     char name[16];
145     if (!s)
146         return;
147     name[sizeof(name) - 1] = 0;
148     strncpy(name, s, sizeof(name));
149     /* Could rewrite argv[0] too, but that's a bit more complicated.
150        This simple way is enough for `top'. */
151     if (prctl(PR_SET_NAME, name)) {
152         perror("unable to change process name");
153         exit(1);
154     }
155 #else
156     fprintf(stderr, "Change of process name not supported by your OS\n");
157     exit(1);
158 #endif
159 }
160 
161 /*
162  * Parse OS specific command line options.
163  * return 0 if option handled, -1 otherwise
164  */
165 void os_parse_cmd_args(int index, const char *optarg)
166 {
167     switch (index) {
168 #ifdef CONFIG_SLIRP
169     case QEMU_OPTION_smb:
170         if (net_slirp_smb(optarg) < 0)
171             exit(1);
172         break;
173 #endif
174     case QEMU_OPTION_runas:
175         user_pwd = getpwnam(optarg);
176         if (!user_pwd) {
177             fprintf(stderr, "User \"%s\" doesn't exist\n", optarg);
178             exit(1);
179         }
180         break;
181     case QEMU_OPTION_chroot:
182         chroot_dir = optarg;
183         break;
184     case QEMU_OPTION_daemonize:
185         daemonize = 1;
186         break;
187     }
188     return;
189 }
190 
191 static void change_process_uid(void)
192 {
193     if (user_pwd) {
194         if (setgid(user_pwd->pw_gid) < 0) {
195             fprintf(stderr, "Failed to setgid(%d)\n", user_pwd->pw_gid);
196             exit(1);
197         }
198         if (initgroups(user_pwd->pw_name, user_pwd->pw_gid) < 0) {
199             fprintf(stderr, "Failed to initgroups(\"%s\", %d)\n",
200                     user_pwd->pw_name, user_pwd->pw_gid);
201             exit(1);
202         }
203         if (setuid(user_pwd->pw_uid) < 0) {
204             fprintf(stderr, "Failed to setuid(%d)\n", user_pwd->pw_uid);
205             exit(1);
206         }
207         if (setuid(0) != -1) {
208             fprintf(stderr, "Dropping privileges failed\n");
209             exit(1);
210         }
211     }
212 }
213 
214 static void change_root(void)
215 {
216     if (chroot_dir) {
217         if (chroot(chroot_dir) < 0) {
218             fprintf(stderr, "chroot failed\n");
219             exit(1);
220         }
221         if (chdir("/")) {
222             perror("not able to chdir to /");
223             exit(1);
224         }
225     }
226 
227 }
228 
229 void os_daemonize(void)
230 {
231     if (daemonize) {
232 	pid_t pid;
233 
234 	if (pipe(fds) == -1)
235 	    exit(1);
236 
237 	pid = fork();
238 	if (pid > 0) {
239 	    uint8_t status;
240 	    ssize_t len;
241 
242 	    close(fds[1]);
243 
244 	again:
245             len = read(fds[0], &status, 1);
246             if (len == -1 && (errno == EINTR))
247                 goto again;
248 
249             if (len != 1)
250                 exit(1);
251             else if (status == 1) {
252                 fprintf(stderr, "Could not acquire pidfile: %s\n", strerror(errno));
253                 exit(1);
254             } else
255                 exit(0);
256 	} else if (pid < 0)
257             exit(1);
258 
259 	close(fds[0]);
260 	qemu_set_cloexec(fds[1]);
261 
262 	setsid();
263 
264 	pid = fork();
265 	if (pid > 0)
266 	    exit(0);
267 	else if (pid < 0)
268 	    exit(1);
269 
270 	umask(027);
271 
272         signal(SIGTSTP, SIG_IGN);
273         signal(SIGTTOU, SIG_IGN);
274         signal(SIGTTIN, SIG_IGN);
275     }
276 }
277 
278 void os_setup_post(void)
279 {
280     int fd = 0;
281 
282     if (daemonize) {
283 	uint8_t status = 0;
284 	ssize_t len;
285 
286     again1:
287 	len = write(fds[1], &status, 1);
288 	if (len == -1 && (errno == EINTR))
289 	    goto again1;
290 
291 	if (len != 1)
292 	    exit(1);
293 
294         if (chdir("/")) {
295             perror("not able to chdir to /");
296             exit(1);
297         }
298 	TFR(fd = qemu_open("/dev/null", O_RDWR));
299 	if (fd == -1)
300 	    exit(1);
301     }
302 
303     change_root();
304     change_process_uid();
305 
306     if (daemonize) {
307         dup2(fd, 0);
308         dup2(fd, 1);
309         dup2(fd, 2);
310 
311         close(fd);
312     }
313 }
314 
315 void os_pidfile_error(void)
316 {
317     if (daemonize) {
318         uint8_t status = 1;
319         if (write(fds[1], &status, 1) != 1) {
320             perror("daemonize. Writing to pipe\n");
321         }
322     } else
323         fprintf(stderr, "Could not acquire pid file: %s\n", strerror(errno));
324 }
325 
326 void os_set_line_buffering(void)
327 {
328     setvbuf(stdout, NULL, _IOLBF, 0);
329 }
330 
331 int qemu_create_pidfile(const char *filename)
332 {
333     char buffer[128];
334     int len;
335     int fd;
336 
337     fd = qemu_open(filename, O_RDWR | O_CREAT, 0600);
338     if (fd == -1) {
339         return -1;
340     }
341     if (lockf(fd, F_TLOCK, 0) == -1) {
342         close(fd);
343         return -1;
344     }
345     len = snprintf(buffer, sizeof(buffer), FMT_pid "\n", getpid());
346     if (write(fd, buffer, len) != len) {
347         close(fd);
348         return -1;
349     }
350 
351     close(fd);
352     return 0;
353 }
354