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