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