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