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 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 }