os-posix.c

   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 <libgen.h>
  35
  36 /* Needed early for CONFIG_BSD etc. */
  37 #include "config-host.h"
  38 #include "sysemu.h"
  39 #include "net/slirp.h"
  40 #include "qemu-options.h"
  41
  42 #ifdef CONFIG_LINUX
  43 #include <sys/prctl.h>
  44 #include <sys/syscall.h>
  45 #endif
  46
  47 #ifdef CONFIG_EVENTFD
  48 #include <sys/eventfd.h>
  49 #endif
  50
  51 static struct passwd *user_pwd;
  52 static const char *chroot_dir;
  53 static int daemonize;
  54 static int fds[2];
  55
  56 void os_setup_early_signal_handling(void)
  57 {
  58     struct sigaction act;
  59     sigfillset(&act.sa_mask);
  60     act.sa_flags = 0;
  61     act.sa_handler = SIG_IGN;
  62     sigaction(SIGPIPE, &act, NULL);
  63 }
  64
  65 static void termsig_handler(int signal, siginfo_t *info, void *c)
  66 {
  67     qemu_system_killed(info->si_signo, info->si_pid);
  68 }
  69
  70 static void sigchld_handler(int signal)
  71 {
  72     waitpid(-1, NULL, WNOHANG);
  73 }
  74
  75 void os_setup_signal_handling(void)
  76 {
  77     struct sigaction act;
  78
  79     memset(&act, 0, sizeof(act));
  80     act.sa_sigaction = termsig_handler;
  81     act.sa_flags = SA_SIGINFO;
  82     sigaction(SIGINT,  &act, NULL);
  83     sigaction(SIGHUP,  &act, NULL);
  84     sigaction(SIGTERM, &act, NULL);
  85
  86     act.sa_handler = sigchld_handler;
  87     act.sa_flags = SA_NOCLDSTOP;
  88     sigaction(SIGCHLD, &act, NULL);
  89 }
  90
  91 /* Find a likely location for support files using the location of the binary.
  92    For installed binaries this will be "$bindir/../share/qemu".  When
  93    running from the build tree this will be "$bindir/../pc-bios".  */
  94 #define SHARE_SUFFIX "/share/qemu"
  95 #define BUILD_SUFFIX "/pc-bios"
  96 char *os_find_datadir(const char *argv0)
  97 {
  98     char *dir;
  99     char *p = NULL;
 100     char *res;
 101     char buf[PATH_MAX];
 102     size_t max_len;
 103
 104 #if defined(__linux__)
 105     {
 106         int len;
 107         len = readlink("/proc/self/exe", buf, sizeof(buf) - 1);
 108         if (len > 0) {
 109             buf[len] = 0;
 110             p = buf;
 111         }
 112     }
 113 #elif defined(__FreeBSD__)
 114     {
 115         static int mib[4] = {CTL_KERN, KERN_PROC, KERN_PROC_PATHNAME, -1};
 116         size_t len = sizeof(buf) - 1;
 117
 118         *buf = '\0';
 119         if (!sysctl(mib, ARRAY_SIZE(mib), buf, &len, NULL, 0) &&
 120             *buf) {
 121             buf[sizeof(buf) - 1] = '\0';
 122             p = buf;
 123         }
 124     }
 125 #endif
 126     /* If we don't have any way of figuring out the actual executable
 127        location then try argv[0].  */
 128     if (!p) {
 129         p = realpath(argv0, buf);
 130         if (!p) {
 131             return NULL;
 132         }
 133     }
 134     dir = dirname(p);
 135     dir = dirname(dir);
 136
 137     max_len = strlen(dir) +
 138         MAX(strlen(SHARE_SUFFIX), strlen(BUILD_SUFFIX)) + 1;
 139     res = qemu_mallocz(max_len);
 140     snprintf(res, max_len, "%s%s", dir, SHARE_SUFFIX);
 141     if (access(res, R_OK)) {
 142         snprintf(res, max_len, "%s%s", dir, BUILD_SUFFIX);
 143         if (access(res, R_OK)) {
 144             qemu_free(res);
 145             res = NULL;
 146         }
 147     }
 148
 149     return res;
 150 }
 151 #undef SHARE_SUFFIX
 152 #undef BUILD_SUFFIX
 153
 154 void os_set_proc_name(const char *s)
 155 {
 156 #if defined(PR_SET_NAME)
 157     char name[16];
 158     if (!s)
 159         return;
 160     name[sizeof(name) - 1] = 0;
 161     strncpy(name, s, sizeof(name));
 162     /* Could rewrite argv[0] too, but that's a bit more complicated.
 163        This simple way is enough for `top'. */
 164     if (prctl(PR_SET_NAME, name)) {
 165         perror("unable to change process name");
 166         exit(1);
 167     }
 168 #else
 169     fprintf(stderr, "Change of process name not supported by your OS\n");
 170     exit(1);
 171 #endif
 172 }
 173
 174 /*
 175  * Parse OS specific command line options.
 176  * return 0 if option handled, -1 otherwise
 177  */
 178 void os_parse_cmd_args(int index, const char *optarg)
 179 {
 180     switch (index) {
 181 #ifdef CONFIG_SLIRP
 182     case QEMU_OPTION_smb:
 183         if (net_slirp_smb(optarg) < 0)
 184             exit(1);
 185         break;
 186 #endif
 187     case QEMU_OPTION_runas:
 188         user_pwd = getpwnam(optarg);
 189         if (!user_pwd) {
 190             fprintf(stderr, "User \"%s\" doesn't exist\n", optarg);
 191             exit(1);
 192         }
 193         break;
 194     case QEMU_OPTION_chroot:
 195         chroot_dir = optarg;
 196         break;
 197     case QEMU_OPTION_daemonize:
 198         daemonize = 1;
 199         break;
 200     }
 201     return;
 202 }
 203
 204 static void change_process_uid(void)
 205 {
 206     if (user_pwd) {
 207         if (setgid(user_pwd->pw_gid) < 0) {
 208             fprintf(stderr, "Failed to setgid(%d)\n", user_pwd->pw_gid);
 209             exit(1);
 210         }
 211         if (setuid(user_pwd->pw_uid) < 0) {
 212             fprintf(stderr, "Failed to setuid(%d)\n", user_pwd->pw_uid);
 213             exit(1);
 214         }
 215         if (setuid(0) != -1) {
 216             fprintf(stderr, "Dropping privileges failed\n");
 217             exit(1);
 218         }
 219     }
 220 }
 221
 222 static void change_root(void)
 223 {
 224     if (chroot_dir) {
 225         if (chroot(chroot_dir) < 0) {
 226             fprintf(stderr, "chroot failed\n");
 227             exit(1);
 228         }
 229         if (chdir("/")) {
 230             perror("not able to chdir to /");
 231             exit(1);
 232         }
 233     }
 234
 235 }
 236
 237 void os_daemonize(void)
 238 {
 239     if (daemonize) {
 240         pid_t pid;
 241
 242         if (pipe(fds) == -1)
 243             exit(1);
 244
 245         pid = fork();
 246         if (pid > 0) {
 247             uint8_t status;
 248             ssize_t len;
 249
 250             close(fds[1]);
 251
 252         again:
 253             len = read(fds[0], &status, 1);
 254             if (len == -1 && (errno == EINTR))
 255                 goto again;
 256
 257             if (len != 1)
 258                 exit(1);
 259             else if (status == 1) {
 260                 fprintf(stderr, "Could not acquire pidfile: %s\n", strerror(errno));
 261                 exit(1);
 262             } else
 263                 exit(0);
 264         } else if (pid < 0)
 265             exit(1);
 266
 267         close(fds[0]);
 268         qemu_set_cloexec(fds[1]);
 269
 270         setsid();
 271
 272         pid = fork();
 273         if (pid > 0)
 274             exit(0);
 275         else if (pid < 0)
 276             exit(1);
 277
 278         umask(027);
 279
 280         signal(SIGTSTP, SIG_IGN);
 281         signal(SIGTTOU, SIG_IGN);
 282         signal(SIGTTIN, SIG_IGN);
 283     }
 284 }
 285
 286 void os_setup_post(void)
 287 {
 288     int fd = 0;
 289
 290     if (daemonize) {
 291         uint8_t status = 0;
 292         ssize_t len;
 293
 294     again1:
 295         len = write(fds[1], &status, 1);
 296         if (len == -1 && (errno == EINTR))
 297             goto again1;
 298
 299         if (len != 1)
 300             exit(1);
 301
 302         if (chdir("/")) {
 303             perror("not able to chdir to /");
 304             exit(1);
 305         }
 306         TFR(fd = qemu_open("/dev/null", O_RDWR));
 307         if (fd == -1)
 308             exit(1);
 309     }
 310
 311     change_root();
 312     change_process_uid();
 313
 314     if (daemonize) {
 315         dup2(fd, 0);
 316         dup2(fd, 1);
 317         dup2(fd, 2);
 318
 319         close(fd);
 320     }
 321 }
 322
 323 void os_pidfile_error(void)
 324 {
 325     if (daemonize) {
 326         uint8_t status = 1;
 327         if (write(fds[1], &status, 1) != 1) {
 328             perror("daemonize. Writing to pipe\n");
 329         }
 330     } else
 331         fprintf(stderr, "Could not acquire pid file: %s\n", strerror(errno));
 332 }
 333
 334 void os_set_line_buffering(void)
 335 {
 336     setvbuf(stdout, NULL, _IOLBF, 0);
 337 }
 338
 339 /*
 340  * Creates an eventfd that looks like a pipe and has EFD_CLOEXEC set.
 341  */
 342 int qemu_eventfd(int fds[2])
 343 {
 344 #ifdef CONFIG_EVENTFD
 345     int ret;
 346
 347     ret = eventfd(0, 0);
 348     if (ret >= 0) {
 349         fds[0] = ret;
 350         qemu_set_cloexec(ret);
 351         if ((fds[1] = dup(ret)) == -1) {
 352             close(ret);
 353             return -1;
 354         }
 355         qemu_set_cloexec(fds[1]);
 356         return 0;
 357     }
 358
 359     if (errno != ENOSYS) {
 360         return -1;
 361     }
 362 #endif
 363
 364     return qemu_pipe(fds);
 365 }
 366
 367 int qemu_create_pidfile(const char *filename)
 368 {
 369     char buffer[128];
 370     int len;
 371     int fd;
 372
 373     fd = qemu_open(filename, O_RDWR | O_CREAT, 0600);
 374     if (fd == -1) {
 375         return -1;
 376     }
 377     if (lockf(fd, F_TLOCK, 0) == -1) {
 378         return -1;
 379     }
 380     len = snprintf(buffer, sizeof(buffer), "%ld\n", (long)getpid());
 381     if (write(fd, buffer, len) != len) {
 382         return -1;
 383     }
 384
 385     return 0;
 386 }
 387
 388 int qemu_get_thread_id(void)
 389 {
 390 #if defined (__linux__)
 391     return syscall(SYS_gettid);
 392 #else
 393     return getpid();
 394 #endif
 395 }