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