Annotation of qemu/os-posix.c, revision 1.1.1.2

1.1       root        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: 
1.1.1.2 ! root       46: #ifdef CONFIG_EVENTFD
        !            47: #include <sys/eventfd.h>
        !            48: #endif
        !            49: 
1.1       root       50: static struct passwd *user_pwd;
                     51: static const char *chroot_dir;
                     52: static int daemonize;
                     53: static int fds[2];
                     54: 
                     55: void os_setup_early_signal_handling(void)
                     56: {
                     57:     struct sigaction act;
                     58:     sigfillset(&act.sa_mask);
                     59:     act.sa_flags = 0;
                     60:     act.sa_handler = SIG_IGN;
                     61:     sigaction(SIGPIPE, &act, NULL);
                     62: }
                     63: 
                     64: static void termsig_handler(int signal)
                     65: {
                     66:     qemu_system_shutdown_request();
                     67: }
                     68: 
                     69: static void sigchld_handler(int signal)
                     70: {
                     71:     waitpid(-1, NULL, WNOHANG);
                     72: }
                     73: 
                     74: void os_setup_signal_handling(void)
                     75: {
                     76:     struct sigaction act;
                     77: 
                     78:     memset(&act, 0, sizeof(act));
                     79:     act.sa_handler = termsig_handler;
                     80:     sigaction(SIGINT,  &act, NULL);
                     81:     sigaction(SIGHUP,  &act, NULL);
                     82:     sigaction(SIGTERM, &act, NULL);
                     83: 
                     84:     act.sa_handler = sigchld_handler;
                     85:     act.sa_flags = SA_NOCLDSTOP;
                     86:     sigaction(SIGCHLD, &act, NULL);
                     87: }
                     88: 
                     89: /* Find a likely location for support files using the location of the binary.
                     90:    For installed binaries this will be "$bindir/../share/qemu".  When
                     91:    running from the build tree this will be "$bindir/../pc-bios".  */
                     92: #define SHARE_SUFFIX "/share/qemu"
                     93: #define BUILD_SUFFIX "/pc-bios"
                     94: char *os_find_datadir(const char *argv0)
                     95: {
                     96:     char *dir;
                     97:     char *p = NULL;
                     98:     char *res;
                     99:     char buf[PATH_MAX];
                    100:     size_t max_len;
                    101: 
                    102: #if defined(__linux__)
                    103:     {
                    104:         int len;
                    105:         len = readlink("/proc/self/exe", buf, sizeof(buf) - 1);
                    106:         if (len > 0) {
                    107:             buf[len] = 0;
                    108:             p = buf;
                    109:         }
                    110:     }
                    111: #elif defined(__FreeBSD__)
                    112:     {
                    113:         static int mib[4] = {CTL_KERN, KERN_PROC, KERN_PROC_PATHNAME, -1};
                    114:         size_t len = sizeof(buf) - 1;
                    115: 
                    116:         *buf = '\0';
1.1.1.2 ! root      117:         if (!sysctl(mib, ARRAY_SIZE(mib), buf, &len, NULL, 0) &&
1.1       root      118:             *buf) {
                    119:             buf[sizeof(buf) - 1] = '\0';
                    120:             p = buf;
                    121:         }
                    122:     }
                    123: #endif
                    124:     /* If we don't have any way of figuring out the actual executable
                    125:        location then try argv[0].  */
                    126:     if (!p) {
                    127:         p = realpath(argv0, buf);
                    128:         if (!p) {
                    129:             return NULL;
                    130:         }
                    131:     }
                    132:     dir = dirname(p);
                    133:     dir = dirname(dir);
                    134: 
                    135:     max_len = strlen(dir) +
                    136:         MAX(strlen(SHARE_SUFFIX), strlen(BUILD_SUFFIX)) + 1;
                    137:     res = qemu_mallocz(max_len);
                    138:     snprintf(res, max_len, "%s%s", dir, SHARE_SUFFIX);
                    139:     if (access(res, R_OK)) {
                    140:         snprintf(res, max_len, "%s%s", dir, BUILD_SUFFIX);
                    141:         if (access(res, R_OK)) {
                    142:             qemu_free(res);
                    143:             res = NULL;
                    144:         }
                    145:     }
                    146: 
                    147:     return res;
                    148: }
                    149: #undef SHARE_SUFFIX
                    150: #undef BUILD_SUFFIX
                    151: 
                    152: void os_set_proc_name(const char *s)
                    153: {
                    154: #if defined(PR_SET_NAME)
                    155:     char name[16];
                    156:     if (!s)
                    157:         return;
                    158:     name[sizeof(name) - 1] = 0;
                    159:     strncpy(name, s, sizeof(name));
                    160:     /* Could rewrite argv[0] too, but that's a bit more complicated.
                    161:        This simple way is enough for `top'. */
                    162:     if (prctl(PR_SET_NAME, name)) {
                    163:         perror("unable to change process name");
                    164:         exit(1);
                    165:     }
                    166: #else
                    167:     fprintf(stderr, "Change of process name not supported by your OS\n");
                    168:     exit(1);
                    169: #endif
                    170: }
                    171: 
                    172: /*
                    173:  * Parse OS specific command line options.
                    174:  * return 0 if option handled, -1 otherwise
                    175:  */
                    176: void os_parse_cmd_args(int index, const char *optarg)
                    177: {
                    178:     switch (index) {
                    179: #ifdef CONFIG_SLIRP
                    180:     case QEMU_OPTION_smb:
                    181:         if (net_slirp_smb(optarg) < 0)
                    182:             exit(1);
                    183:         break;
                    184: #endif
                    185:     case QEMU_OPTION_runas:
                    186:         user_pwd = getpwnam(optarg);
                    187:         if (!user_pwd) {
                    188:             fprintf(stderr, "User \"%s\" doesn't exist\n", optarg);
                    189:             exit(1);
                    190:         }
                    191:         break;
                    192:     case QEMU_OPTION_chroot:
                    193:         chroot_dir = optarg;
                    194:         break;
                    195:     case QEMU_OPTION_daemonize:
                    196:         daemonize = 1;
                    197:         break;
                    198:     }
                    199:     return;
                    200: }
                    201: 
                    202: static void change_process_uid(void)
                    203: {
                    204:     if (user_pwd) {
                    205:         if (setgid(user_pwd->pw_gid) < 0) {
                    206:             fprintf(stderr, "Failed to setgid(%d)\n", user_pwd->pw_gid);
                    207:             exit(1);
                    208:         }
                    209:         if (setuid(user_pwd->pw_uid) < 0) {
                    210:             fprintf(stderr, "Failed to setuid(%d)\n", user_pwd->pw_uid);
                    211:             exit(1);
                    212:         }
                    213:         if (setuid(0) != -1) {
                    214:             fprintf(stderr, "Dropping privileges failed\n");
                    215:             exit(1);
                    216:         }
                    217:     }
                    218: }
                    219: 
                    220: static void change_root(void)
                    221: {
                    222:     if (chroot_dir) {
                    223:         if (chroot(chroot_dir) < 0) {
                    224:             fprintf(stderr, "chroot failed\n");
                    225:             exit(1);
                    226:         }
                    227:         if (chdir("/")) {
                    228:             perror("not able to chdir to /");
                    229:             exit(1);
                    230:         }
                    231:     }
                    232: 
                    233: }
                    234: 
                    235: void os_daemonize(void)
                    236: {
                    237:     if (daemonize) {
                    238:        pid_t pid;
                    239: 
                    240:        if (pipe(fds) == -1)
                    241:            exit(1);
                    242: 
                    243:        pid = fork();
                    244:        if (pid > 0) {
                    245:            uint8_t status;
                    246:            ssize_t len;
                    247: 
                    248:            close(fds[1]);
                    249: 
                    250:        again:
                    251:             len = read(fds[0], &status, 1);
                    252:             if (len == -1 && (errno == EINTR))
                    253:                 goto again;
                    254: 
                    255:             if (len != 1)
                    256:                 exit(1);
                    257:             else if (status == 1) {
                    258:                 fprintf(stderr, "Could not acquire pidfile: %s\n", strerror(errno));
                    259:                 exit(1);
                    260:             } else
                    261:                 exit(0);
                    262:        } else if (pid < 0)
                    263:             exit(1);
                    264: 
                    265:        close(fds[0]);
                    266:        qemu_set_cloexec(fds[1]);
                    267: 
                    268:        setsid();
                    269: 
                    270:        pid = fork();
                    271:        if (pid > 0)
                    272:            exit(0);
                    273:        else if (pid < 0)
                    274:            exit(1);
                    275: 
                    276:        umask(027);
                    277: 
                    278:         signal(SIGTSTP, SIG_IGN);
                    279:         signal(SIGTTOU, SIG_IGN);
                    280:         signal(SIGTTIN, SIG_IGN);
                    281:     }
                    282: }
                    283: 
                    284: void os_setup_post(void)
                    285: {
                    286:     int fd = 0;
                    287: 
                    288:     if (daemonize) {
                    289:        uint8_t status = 0;
                    290:        ssize_t len;
                    291: 
                    292:     again1:
                    293:        len = write(fds[1], &status, 1);
                    294:        if (len == -1 && (errno == EINTR))
                    295:            goto again1;
                    296: 
                    297:        if (len != 1)
                    298:            exit(1);
                    299: 
                    300:         if (chdir("/")) {
                    301:             perror("not able to chdir to /");
                    302:             exit(1);
                    303:         }
                    304:        TFR(fd = qemu_open("/dev/null", O_RDWR));
                    305:        if (fd == -1)
                    306:            exit(1);
                    307:     }
                    308: 
                    309:     change_root();
                    310:     change_process_uid();
                    311: 
                    312:     if (daemonize) {
                    313:         dup2(fd, 0);
                    314:         dup2(fd, 1);
                    315:         dup2(fd, 2);
                    316: 
                    317:         close(fd);
                    318:     }
                    319: }
                    320: 
                    321: void os_pidfile_error(void)
                    322: {
                    323:     if (daemonize) {
                    324:         uint8_t status = 1;
                    325:         if (write(fds[1], &status, 1) != 1) {
                    326:             perror("daemonize. Writing to pipe\n");
                    327:         }
                    328:     } else
                    329:         fprintf(stderr, "Could not acquire pid file: %s\n", strerror(errno));
                    330: }
                    331: 
                    332: void os_set_line_buffering(void)
                    333: {
                    334:     setvbuf(stdout, NULL, _IOLBF, 0);
                    335: }
1.1.1.2 ! root      336: 
        !           337: /*
        !           338:  * Creates an eventfd that looks like a pipe and has EFD_CLOEXEC set.
        !           339:  */
        !           340: int qemu_eventfd(int fds[2])
        !           341: {
        !           342: #ifdef CONFIG_EVENTFD
        !           343:     int ret;
        !           344: 
        !           345:     ret = eventfd(0, 0);
        !           346:     if (ret >= 0) {
        !           347:         fds[0] = ret;
        !           348:         qemu_set_cloexec(ret);
        !           349:         if ((fds[1] = dup(ret)) == -1) {
        !           350:             close(ret);
        !           351:             return -1;
        !           352:         }
        !           353:         qemu_set_cloexec(fds[1]);
        !           354:         return 0;
        !           355:     }
        !           356: 
        !           357:     if (errno != ENOSYS) {
        !           358:         return -1;
        !           359:     }
        !           360: #endif
        !           361: 
        !           362:     return qemu_pipe(fds);
        !           363: }
        !           364: 
        !           365: int qemu_create_pidfile(const char *filename)
        !           366: {
        !           367:     char buffer[128];
        !           368:     int len;
        !           369:     int fd;
        !           370: 
        !           371:     fd = qemu_open(filename, O_RDWR | O_CREAT, 0600);
        !           372:     if (fd == -1) {
        !           373:         return -1;
        !           374:     }
        !           375:     if (lockf(fd, F_TLOCK, 0) == -1) {
        !           376:         return -1;
        !           377:     }
        !           378:     len = snprintf(buffer, sizeof(buffer), "%ld\n", (long)getpid());
        !           379:     if (write(fd, buffer, len) != len) {
        !           380:         return -1;
        !           381:     }
        !           382: 
        !           383:     return 0;
        !           384: }

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