udev: avoid creating /dev/kmsg with fopen() to support CONFIG_PRINTK=n

4 files changed, 29 insertions, 20 deletions

diff --git a/src/libudev/libudev-private.h b/src/libudev/libudev-private.h
index 4eb4a598e0..bc58424636 100644
--- a/src/libudev/libudev-private.h
+++ b/src/libudev/libudev-private.h
@@ -173,4 +173,5 @@ int util_resolve_subsys_kernel(struct udev *udev, const char *string,
                                       char *result, size_t maxsize, int read_value);
 unsigned long long ts_usec(const struct timespec *ts);
 unsigned long long now_usec(void);
+ssize_t print_kmsg(const char *fmt, ...) __attribute__((format(printf, 1, 2)));
 #endif
diff --git a/src/libudev/libudev-util.c b/src/libudev/libudev-util.c
index 8e6d5b621d..e2fb449d64 100644
--- a/src/libudev/libudev-util.c
+++ b/src/libudev/libudev-util.c
@@ -727,3 +727,28 @@ unsigned long long now_usec(void)
                 return 0;
         return ts_usec(&ts);
 }
+
+ssize_t print_kmsg(const char *fmt, ...)
+{
+        int fd;
+        va_list ap;
+        char text[1024];
+        ssize_t len;
+        ssize_t ret;
+
+        fd = open("/dev/kmsg", O_WRONLY|O_NOCTTY|O_CLOEXEC);
+        if (fd < 0)
+                return -errno;
+
+        len = snprintf(text, sizeof(text), "<30>systemd-udevd[%u]: ", getpid());
+
+        va_start(ap, fmt);
+        len += vsnprintf(text + len, sizeof(text) - len, fmt, ap);
+        va_end(ap);
+
+        ret = write(fd, text, len);
+        if (ret < 0)
+                ret = -errno;
+        close(fd);
+        return ret;
+}
diff --git a/src/udev/udev-event.c b/src/udev/udev-event.c
index 46e579dce2..d5dd1f3ba4 100644
--- a/src/udev/udev-event.c
+++ b/src/udev/udev-event.c
@@ -767,14 +767,7 @@ static int rename_netif(struct udev_event *event)
         util_strscpy(ifr.ifr_newname, IFNAMSIZ, event->name);
         err = ioctl(sk, SIOCSIFNAME, &ifr);
         if (err >= 0) {
-                FILE *f;
-
-                f = fopen("/dev/kmsg", "we");
-                if (f != NULL) {
-                        fprintf(f, "<30>systemd-udevd[%u]: renamed network interface %s to %s\n",
-                                getpid(), ifr.ifr_name, ifr.ifr_newname);
-                        fclose(f);
-                }
+                print_kmsg("renamed network interface %s to %s", ifr.ifr_name, ifr.ifr_newname);
         } else {
                 err = -errno;
                 log_error("error changing net interface name %s to %s: %m\n", ifr.ifr_name, ifr.ifr_newname);
diff --git a/src/udev/udevd.c b/src/udev/udevd.c
index ee78b396b7..a028c9cac0 100644
--- a/src/udev/udevd.c
+++ b/src/udev/udevd.c
@@ -891,7 +891,6 @@ static int mem_size_mb(void)
 static int convert_db(struct udev *udev)
 {
         char filename[UTIL_PATH_SIZE];
-        FILE *f;
         struct udev_enumerate *udev_enumerate;
         struct udev_list_entry *list_entry;
 
@@ -907,11 +906,7 @@ static int convert_db(struct udev *udev)
         if (access(filename, F_OK) < 0)
                 return 0;
 
-        f = fopen("/dev/kmsg", "we");
-        if (f != NULL) {
-                fprintf(f, "<30>systemd-udevd[%u]: converting old udev database\n", getpid());
-                fclose(f);
-        }
+        print_kmsg("converting old udev database\n");
 
         udev_enumerate = udev_enumerate_new(udev);
         if (udev_enumerate == NULL)
@@ -1058,7 +1053,6 @@ static void kernel_cmdline_options(struct udev *udev)
 int main(int argc, char *argv[])
 {
         struct udev *udev;
-        FILE *f;
         sigset_t mask;
         int daemonize = false;
         int resolve_names = 1;
@@ -1265,11 +1259,7 @@ int main(int argc, char *argv[])
                 sd_notify(1, "READY=1");
         }
 
-        f = fopen("/dev/kmsg", "we");
-        if (f != NULL) {
-                fprintf(f, "<30>systemd-udevd[%u]: starting version " VERSION "\n", getpid());
-                fclose(f);
-        }
+        print_kmsg("starting version " VERSION "\n");
 
         if (!debug) {
                 int fd;