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

2 files changed, 26 insertions, 0 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;
+}