1 files changed, 35 insertions, 0 deletions
diff --git a/lib/libc/gen/uexterr_format.c b/lib/libc/gen/uexterr_format.c
new file mode 100644
index 000000000000..e8ddfbd578e3
--- /dev/null
+++ b/lib/libc/gen/uexterr_format.c
@@ -0,0 +1,35 @@
+/*-
+ * SPDX-License-Identifier: BSD-2-Clause
+ *
+ * Copyright (c) 2025 The FreeBSD Foundation
+ * All rights reserved.
+ *
+ * This software were developed by Konstantin Belousov <kib@FreeBSD.org>
+ * under sponsorship from the FreeBSD Foundation.
+ */
+
+#include <sys/types.h>
+#include <sys/exterrvar.h>
+#include <exterr.h>
+#include <stdio.h>
+#include <string.h>
+
+int
+__uexterr_format(const struct uexterror *ue, char *buf, size_t bufsz)
+{
+	if (bufsz > UEXTERROR_MAXLEN)
+		bufsz = UEXTERROR_MAXLEN;
+	if (ue->error == 0) {
+		strlcpy(buf, "", bufsz);
+		return (0);
+	}
+	if (ue->msg[0] == '\0') {
+		snprintf(buf, bufsz,
+		    "errno %d category %u (src line %u) p1 %#jx p2 %#jx",
+		    ue->error, ue->cat, ue->src_line,
+		    (uintmax_t)ue->p1, (uintmax_t)ue->p2);
+	} else {
+		strlcpy(buf, ue->msg, bufsz);
+	}
+	return (0);
+}