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 #endif
  46
  47 #ifdef __FreeBSD__
  48 #include <sys/sysctl.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 void os_setup_signal_handling(void)
  71 {
  72     struct sigaction act;
  73
  74     memset(&act, 0, sizeof(act));
  75     act.sa_sigaction = termsig_handler;
  76     act.sa_flags = SA_SIGINFO;
  77     sigaction(SIGINT,  &act, NULL);
  78     sigaction(SIGHUP,  &act, NULL);
  79     sigaction(SIGTERM, &act, NULL);
  80 }
  81
  82 /* Find a likely location for support files using the location of the binary.
  83    For installed binaries this will be "$bindir/../share/qemu".  When
  84    running from the build tree this will be "$bindir/../pc-bios".  */
  85 #define SHARE_SUFFIX "/share/qemu"
  86 #define BUILD_SUFFIX "/pc-bios"
  87 char *os_find_datadir(const char *argv0)
  88 {
  89     char *dir;
  90     char *p = NULL;
  91     char *res;
  92     char buf[PATH_MAX];
  93     size_t max_len;
  94
  95 #if defined(__linux__)
  96     {
  97         int len;
  98         len = readlink("/proc/self/exe", buf, sizeof(buf) - 1);
  99         if (len > 0) {
 100             buf[len] = 0;
 101             p = buf;
 102         }
 103     }
 104 #elif defined(__FreeBSD__)
 105     {
 106         static int mib[4] = {CTL_KERN, KERN_PROC, KERN_PROC_PATHNAME, -1};
 107         size_t len = sizeof(buf) - 1;
 108
 109         *buf = '\0';
 110         if (!sysctl(mib, ARRAY_SIZE(mib), buf, &len, NULL, 0) &&
 111             *buf) {
 112             buf[sizeof(buf) - 1] = '\0';
 113             p = buf;
 114         }
 115     }
 116 #endif
 117     /* If we don't have any way of figuring out the actual executable
 118        location then try argv[0].  */
 119     if (!p) {
 120         p = realpath(argv0, buf);
 121         if (!p) {
 122             return NULL;
 123         }
 124     }
 125     dir = dirname(p);
 126     dir = dirname(dir);
 127
 128     max_len = strlen(dir) +
 129         MAX(strlen(SHARE_SUFFIX), strlen(BUILD_SUFFIX)) + 1;
 130     res = g_malloc0(max_len);
 131     snprintf(res, max_len, "%s%s", dir, SHARE_SUFFIX);
 132     if (access(res, R_OK)) {
 133         snprintf(res, max_len, "%s%s", dir, BUILD_SUFFIX);
 134         if (access(res, R_OK)) {
 135             g_free(res);
 136             res = NULL;
 137         }
 138     }
 139
 140     return res;
 141 }
 142 #undef SHARE_SUFFIX
 143 #undef BUILD_SUFFIX
 144
 145 void os_set_proc_name(const char *s)
 146 {
 147 #if defined(PR_SET_NAME)
 148     char name[16];
 149     if (!s)
 150         return;
 151     name[sizeof(name) - 1] = 0;
 152     strncpy(name, s, sizeof(name));
 153     /* Could rewrite argv[0] too, but that's a bit more complicated.
 154        This simple way is enough for `top'. */
 155     if (prctl(PR_SET_NAME, name)) {
 156         perror("unable to change process name");
 157         exit(1);
 158     }
 159 #else
 160     fprintf(stderr, "Change of process name not supported by your OS\n");
 161     exit(1);
 162 #endif
 163 }
 164
 165 /*
 166  * Parse OS specific command line options.
 167  * return 0 if option handled, -1 otherwise
 168  */
 169 void os_parse_cmd_args(int index, const char *optarg)
 170 {
 171     switch (index) {
 172 #ifdef CONFIG_SLIRP
 173     case QEMU_OPTION_smb:
 174         if (net_slirp_smb(optarg) < 0)
 175             exit(1);
 176         break;
 177 #endif
 178     case QEMU_OPTION_runas:
 179         user_pwd = getpwnam(optarg);
 180         if (!user_pwd) {
 181             fprintf(stderr, "User \"%s\" doesn't exist\n", optarg);
 182             exit(1);
 183         }
 184         break;
 185     case QEMU_OPTION_chroot:
 186         chroot_dir = optarg;
 187         break;
 188     case QEMU_OPTION_daemonize:
 189         daemonize = 1;
 190         break;
 191     }
 192     return;
 193 }
 194
 195 static void change_process_uid(void)
 196 {
 197     if (user_pwd) {
 198         if (setgid(user_pwd->pw_gid) < 0) {
 199             fprintf(stderr, "Failed to setgid(%d)\n", user_pwd->pw_gid);
 200             exit(1);
 201         }
 202         if (initgroups(user_pwd->pw_name, user_pwd->pw_gid) < 0) {
 203             fprintf(stderr, "Failed to initgroups(\"%s\", %d)\n",
 204                     user_pwd->pw_name, user_pwd->pw_gid);
 205             exit(1);
 206         }
 207         if (setuid(user_pwd->pw_uid) < 0) {
 208             fprintf(stderr, "Failed to setuid(%d)\n", user_pwd->pw_uid);
 209             exit(1);
 210         }
 211         if (setuid(0) != -1) {
 212             fprintf(stderr, "Dropping privileges failed\n");
 213             exit(1);
 214         }
 215     }
 216 }
 217
 218 static void change_root(void)
 219 {
 220     if (chroot_dir) {
 221         if (chroot(chroot_dir) < 0) {
 222             fprintf(stderr, "chroot failed\n");
 223             exit(1);
 224         }
 225         if (chdir("/")) {
 226             perror("not able to chdir to /");
 227             exit(1);
 228         }
 229     }
 230
 231 }
 232
 233 void os_daemonize(void)
 234 {
 235     if (daemonize) {
 236         pid_t pid;
 237
 238         if (pipe(fds) == -1)
 239             exit(1);
 240
 241         pid = fork();
 242         if (pid > 0) {
 243             uint8_t status;
 244             ssize_t len;
 245
 246             close(fds[1]);
 247
 248         again:
 249             len = read(fds[0], &status, 1);
 250             if (len == -1 && (errno == EINTR))
 251                 goto again;
 252
 253             if (len != 1)
 254                 exit(1);
 255             else if (status == 1) {
 256                 fprintf(stderr, "Could not acquire pidfile: %s\n", strerror(errno));
 257                 exit(1);
 258             } else
 259                 exit(0);
 260         } else if (pid < 0)
 261             exit(1);
 262
 263         close(fds[0]);
 264         qemu_set_cloexec(fds[1]);
 265
 266         setsid();
 267
 268         pid = fork();
 269         if (pid > 0)
 270             exit(0);
 271         else if (pid < 0)
 272             exit(1);
 273
 274         umask(027);
 275
 276         signal(SIGTSTP, SIG_IGN);
 277         signal(SIGTTOU, SIG_IGN);
 278         signal(SIGTTIN, SIG_IGN);
 279     }
 280 }
 281
 282 void os_setup_post(void)
 283 {
 284     int fd = 0;
 285
 286     if (daemonize) {
 287         uint8_t status = 0;
 288         ssize_t len;
 289
 290     again1:
 291         len = write(fds[1], &status, 1);
 292         if (len == -1 && (errno == EINTR))
 293             goto again1;
 294
 295         if (len != 1)
 296             exit(1);
 297
 298         if (chdir("/")) {
 299             perror("not able to chdir to /");
 300             exit(1);
 301         }
 302         TFR(fd = qemu_open("/dev/null", O_RDWR));
 303         if (fd == -1)
 304             exit(1);
 305     }
 306
 307     change_root();
 308     change_process_uid();
 309
 310     if (daemonize) {
 311         dup2(fd, 0);
 312         dup2(fd, 1);
 313         dup2(fd, 2);
 314
 315         close(fd);
 316     }
 317 }
 318
 319 void os_pidfile_error(void)
 320 {
 321     if (daemonize) {
 322         uint8_t status = 1;
 323         if (write(fds[1], &status, 1) != 1) {
 324             perror("daemonize. Writing to pipe\n");
 325         }
 326     } else
 327         fprintf(stderr, "Could not acquire pid file: %s\n", strerror(errno));
 328 }
 329
 330 void os_set_line_buffering(void)
 331 {
 332     setvbuf(stdout, NULL, _IOLBF, 0);
 333 }
 334
 335 int qemu_create_pidfile(const char *filename)
 336 {
 337     char buffer[128];
 338     int len;
 339     int fd;
 340
 341     fd = qemu_open(filename, O_RDWR | O_CREAT, 0600);
 342     if (fd == -1) {
 343         return -1;
 344     }
 345     if (lockf(fd, F_TLOCK, 0) == -1) {
 346         close(fd);
 347         return -1;
 348     }
 349     len = snprintf(buffer, sizeof(buffer), FMT_pid "\n", getpid());
 350     if (write(fd, buffer, len) != len) {
 351         close(fd);
 352         return -1;
 353     }
 354
 355     /* keep pidfile open & locked forever */
 356     return 0;
 357 }