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