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 #ifdef CONFIG_LINUX
  41 #include <sys/prctl.h>
  42 #endif
  43
  44 static struct passwd *user_pwd;
  45 static const char *chroot_dir;
  46 static int daemonize;
  47 static int fds[2];
  48
  49 void os_setup_early_signal_handling(void)
  50 {
  51     struct sigaction act;
  52     sigfillset(&act.sa_mask);
  53     act.sa_flags = 0;
  54     act.sa_handler = SIG_IGN;
  55     sigaction(SIGPIPE, &act, NULL);
  56 }
  57
  58 static void termsig_handler(int signal)
  59 {
  60     qemu_system_shutdown_request();
  61 }
  62
  63 static void sigchld_handler(int signal)
  64 {
  65     waitpid(-1, NULL, WNOHANG);
  66 }
  67
  68 void os_setup_signal_handling(void)
  69 {
  70     struct sigaction act;
  71
  72     memset(&act, 0, sizeof(act));
  73     act.sa_handler = termsig_handler;
  74     sigaction(SIGINT,  &act, NULL);
  75     sigaction(SIGHUP,  &act, NULL);
  76     sigaction(SIGTERM, &act, NULL);
  77
  78     act.sa_handler = sigchld_handler;
  79     act.sa_flags = SA_NOCLDSTOP;
  80     sigaction(SIGCHLD, &act, NULL);
  81 }
  82
  83 /* Find a likely location for support files using the location of the binary.
  84    For installed binaries this will be "$bindir/../share/qemu".  When
  85    running from the build tree this will be "$bindir/../pc-bios".  */
  86 #define SHARE_SUFFIX "/share/qemu"
  87 #define BUILD_SUFFIX "/pc-bios"
  88 char *os_find_datadir(const char *argv0)
  89 {
  90     char *dir;
  91     char *p = NULL;
  92     char *res;
  93     char buf[PATH_MAX];
  94     size_t max_len;
  95
  96 #if defined(__linux__)
  97     {
  98         int len;
  99         len = readlink("/proc/self/exe", buf, sizeof(buf) - 1);
 100         if (len > 0) {
 101             buf[len] = 0;
 102             p = buf;
 103         }
 104     }
 105 #elif defined(__FreeBSD__)
 106     {
 107         static int mib[4] = {CTL_KERN, KERN_PROC, KERN_PROC_PATHNAME, -1};
 108         size_t len = sizeof(buf) - 1;
 109
 110         *buf = '\0';
 111         if (!sysctl(mib, sizeof(mib)/sizeof(*mib), buf, &len, NULL, 0) &&
 112             *buf) {
 113             buf[sizeof(buf) - 1] = '\0';
 114             p = buf;
 115         }
 116     }
 117 #endif
 118     /* If we don't have any way of figuring out the actual executable
 119        location then try argv[0].  */
 120     if (!p) {
 121         p = realpath(argv0, buf);
 122         if (!p) {
 123             return NULL;
 124         }
 125     }
 126     dir = dirname(p);
 127     dir = dirname(dir);
 128
 129     max_len = strlen(dir) +
 130         MAX(strlen(SHARE_SUFFIX), strlen(BUILD_SUFFIX)) + 1;
 131     res = qemu_mallocz(max_len);
 132     snprintf(res, max_len, "%s%s", dir, SHARE_SUFFIX);
 133     if (access(res, R_OK)) {
 134         snprintf(res, max_len, "%s%s", dir, BUILD_SUFFIX);
 135         if (access(res, R_OK)) {
 136             qemu_free(res);
 137             res = NULL;
 138         }
 139     }
 140
 141     return res;
 142 }
 143 #undef SHARE_SUFFIX
 144 #undef BUILD_SUFFIX
 145
 146 void os_set_proc_name(const char *s)
 147 {
 148 #if defined(PR_SET_NAME)
 149     char name[16];
 150     if (!s)
 151         return;
 152     name[sizeof(name) - 1] = 0;
 153     strncpy(name, s, sizeof(name));
 154     /* Could rewrite argv[0] too, but that's a bit more complicated.
 155        This simple way is enough for `top'. */
 156     if (prctl(PR_SET_NAME, name)) {
 157         perror("unable to change process name");
 158         exit(1);
 159     }
 160 #else
 161     fprintf(stderr, "Change of process name not supported by your OS\n");
 162     exit(1);
 163 #endif
 164 }
 165
 166 /*
 167  * Parse OS specific command line options.
 168  * return 0 if option handled, -1 otherwise
 169  */
 170 void os_parse_cmd_args(int index, const char *optarg)
 171 {
 172     switch (index) {
 173 #ifdef CONFIG_SLIRP
 174     case QEMU_OPTION_smb:
 175         if (net_slirp_smb(optarg) < 0)
 176             exit(1);
 177         break;
 178 #endif
 179     case QEMU_OPTION_runas:
 180         user_pwd = getpwnam(optarg);
 181         if (!user_pwd) {
 182             fprintf(stderr, "User \"%s\" doesn't exist\n", optarg);
 183             exit(1);
 184         }
 185         break;
 186     case QEMU_OPTION_chroot:
 187         chroot_dir = optarg;
 188         break;
 189     case QEMU_OPTION_daemonize:
 190         daemonize = 1;
 191         break;
 192     }
 193     return;
 194 }
 195
 196 static void change_process_uid(void)
 197 {
 198     if (user_pwd) {
 199         if (setgid(user_pwd->pw_gid) < 0) {
 200             fprintf(stderr, "Failed to setgid(%d)\n", 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 }