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 #include <pwd.h>
  32 #include <libgen.h>
  33
  34 /* Needed early for CONFIG_BSD etc. */
  35 #include "config-host.h"
  36 #include "sysemu.h"
  37 #include "net/slirp.h"
  38 #include "qemu-options.h"
  39
  40 static struct passwd *user_pwd;
  41 static const char *chroot_dir;
  42 static int daemonize;
  43 static int fds[2];
  44
  45 void os_setup_early_signal_handling(void)
  46 {
  47     struct sigaction act;
  48     sigfillset(&act.sa_mask);
  49     act.sa_flags = 0;
  50     act.sa_handler = SIG_IGN;
  51     sigaction(SIGPIPE, &act, NULL);
  52 }
  53
  54 static void termsig_handler(int signal)
  55 {
  56     qemu_system_shutdown_request();
  57 }
  58
  59 static void sigchld_handler(int signal)
  60 {
  61     waitpid(-1, NULL, WNOHANG);
  62 }
  63
  64 void os_setup_signal_handling(void)
  65 {
  66     struct sigaction act;
  67
  68     memset(&act, 0, sizeof(act));
  69     act.sa_handler = termsig_handler;
  70     sigaction(SIGINT,  &act, NULL);
  71     sigaction(SIGHUP,  &act, NULL);
  72     sigaction(SIGTERM, &act, NULL);
  73
  74     act.sa_handler = sigchld_handler;
  75     act.sa_flags = SA_NOCLDSTOP;
  76     sigaction(SIGCHLD, &act, NULL);
  77 }
  78
  79 /* Find a likely location for support files using the location of the binary.
  80    For installed binaries this will be "$bindir/../share/qemu".  When
  81    running from the build tree this will be "$bindir/../pc-bios".  */
  82 #define SHARE_SUFFIX "/share/qemu"
  83 #define BUILD_SUFFIX "/pc-bios"
  84 char *os_find_datadir(const char *argv0)
  85 {
  86     char *dir;
  87     char *p = NULL;
  88     char *res;
  89     char buf[PATH_MAX];
  90     size_t max_len;
  91
  92 #if defined(__linux__)
  93     {
  94         int len;
  95         len = readlink("/proc/self/exe", buf, sizeof(buf) - 1);
  96         if (len > 0) {
  97             buf[len] = 0;
  98             p = buf;
  99         }
 100     }
 101 #elif defined(__FreeBSD__)
 102     {
 103         static int mib[4] = {CTL_KERN, KERN_PROC, KERN_PROC_PATHNAME, -1};
 104         size_t len = sizeof(buf) - 1;
 105
 106         *buf = '\0';
 107         if (!sysctl(mib, sizeof(mib)/sizeof(*mib), buf, &len, NULL, 0) &&
 108             *buf) {
 109             buf[sizeof(buf) - 1] = '\0';
 110             p = buf;
 111         }
 112     }
 113 #endif
 114     /* If we don't have any way of figuring out the actual executable
 115        location then try argv[0].  */
 116     if (!p) {
 117         p = realpath(argv0, buf);
 118         if (!p) {
 119             return NULL;
 120         }
 121     }
 122     dir = dirname(p);
 123     dir = dirname(dir);
 124
 125     max_len = strlen(dir) +
 126         MAX(strlen(SHARE_SUFFIX), strlen(BUILD_SUFFIX)) + 1;
 127     res = qemu_mallocz(max_len);
 128     snprintf(res, max_len, "%s%s", dir, SHARE_SUFFIX);
 129     if (access(res, R_OK)) {
 130         snprintf(res, max_len, "%s%s", dir, BUILD_SUFFIX);
 131         if (access(res, R_OK)) {
 132             qemu_free(res);
 133             res = NULL;
 134         }
 135     }
 136
 137     return res;
 138 }
 139 #undef SHARE_SUFFIX
 140 #undef BUILD_SUFFIX
 141
 142 /*
 143  * Parse OS specific command line options.
 144  * return 0 if option handled, -1 otherwise
 145  */
 146 void os_parse_cmd_args(int index, const char *optarg)
 147 {
 148     switch (index) {
 149 #ifdef CONFIG_SLIRP
 150     case QEMU_OPTION_smb:
 151         if (net_slirp_smb(optarg) < 0)
 152             exit(1);
 153         break;
 154 #endif
 155     case QEMU_OPTION_runas:
 156         user_pwd = getpwnam(optarg);
 157         if (!user_pwd) {
 158             fprintf(stderr, "User \"%s\" doesn't exist\n", optarg);
 159             exit(1);
 160         }
 161         break;
 162     case QEMU_OPTION_chroot:
 163         chroot_dir = optarg;
 164         break;
 165     case QEMU_OPTION_daemonize:
 166         daemonize = 1;
 167         break;
 168     }
 169     return;
 170 }
 171
 172 void os_change_process_uid(void)
 173 {
 174     if (user_pwd) {
 175         if (setgid(user_pwd->pw_gid) < 0) {
 176             fprintf(stderr, "Failed to setgid(%d)\n", user_pwd->pw_gid);
 177             exit(1);
 178         }
 179         if (setuid(user_pwd->pw_uid) < 0) {
 180             fprintf(stderr, "Failed to setuid(%d)\n", user_pwd->pw_uid);
 181             exit(1);
 182         }
 183         if (setuid(0) != -1) {
 184             fprintf(stderr, "Dropping privileges failed\n");
 185             exit(1);
 186         }
 187     }
 188 }
 189
 190 void os_change_root(void)
 191 {
 192     if (chroot_dir) {
 193         if (chroot(chroot_dir) < 0) {
 194             fprintf(stderr, "chroot failed\n");
 195             exit(1);
 196         }
 197         if (chdir("/")) {
 198             perror("not able to chdir to /");
 199             exit(1);
 200         }
 201     }
 202
 203 }
 204
 205 void os_daemonize(void)
 206 {
 207     if (daemonize) {
 208         pid_t pid;
 209
 210         if (pipe(fds) == -1)
 211             exit(1);
 212
 213         pid = fork();
 214         if (pid > 0) {
 215             uint8_t status;
 216             ssize_t len;
 217
 218             close(fds[1]);
 219
 220         again:
 221             len = read(fds[0], &status, 1);
 222             if (len == -1 && (errno == EINTR))
 223                 goto again;
 224
 225             if (len != 1)
 226                 exit(1);
 227             else if (status == 1) {
 228                 fprintf(stderr, "Could not acquire pidfile: %s\n", strerror(errno));
 229                 exit(1);
 230             } else
 231                 exit(0);
 232         } else if (pid < 0)
 233             exit(1);
 234
 235         close(fds[0]);
 236         qemu_set_cloexec(fds[1]);
 237
 238         setsid();
 239
 240         pid = fork();
 241         if (pid > 0)
 242             exit(0);
 243         else if (pid < 0)
 244             exit(1);
 245
 246         umask(027);
 247
 248         signal(SIGTSTP, SIG_IGN);
 249         signal(SIGTTOU, SIG_IGN);
 250         signal(SIGTTIN, SIG_IGN);
 251     }
 252 }
 253
 254 void os_setup_post(void)
 255 {
 256     int fd = 0;
 257
 258     if (daemonize) {
 259         uint8_t status = 0;
 260         ssize_t len;
 261
 262     again1:
 263         len = write(fds[1], &status, 1);
 264         if (len == -1 && (errno == EINTR))
 265             goto again1;
 266
 267         if (len != 1)
 268             exit(1);
 269
 270         if (chdir("/")) {
 271             perror("not able to chdir to /");
 272             exit(1);
 273         }
 274         TFR(fd = qemu_open("/dev/null", O_RDWR));
 275         if (fd == -1)
 276             exit(1);
 277     }
 278
 279     os_change_root();
 280     os_change_process_uid();
 281
 282     if (daemonize) {
 283         dup2(fd, 0);
 284         dup2(fd, 1);
 285         dup2(fd, 2);
 286
 287         close(fd);
 288     }
 289 }
 290
 291 void os_pidfile_error(void)
 292 {
 293     if (daemonize) {
 294         uint8_t status = 1;
 295         if (write(fds[1], &status, 1) != 1) {
 296             perror("daemonize. Writing to pipe\n");
 297         }
 298     } else
 299         fprintf(stderr, "Could not acquire pid file: %s\n", strerror(errno));
 300 }