1 files changed, 86 insertions, 0 deletions
diff --git a/usr/src/cmd/svc/rootisramdisk/rootisramdisk.c b/usr/src/cmd/svc/rootisramdisk/rootisramdisk.c
new file mode 100644
index 0000000000..353be0141a
--- /dev/null
+++ b/usr/src/cmd/svc/rootisramdisk/rootisramdisk.c
@@ -0,0 +1,86 @@
+/*
+ * This file and its contents are supplied under the terms of the
+ * Common Development and Distribution License ("CDDL"), version 1.0.
+ * You may only use this file in accordance with the terms of version
+ * 1.0 of the CDDL.
+ *
+ * A full copy of the text of the CDDL should have accompanied this
+ * source.  A copy of the CDDL is also available via the Internet at
+ * http://www.illumos.org/license/CDDL.
+ */
+
+/*
+ * Copyright 2021 Oxide Computer Company
+ */
+
+/*
+ * rootisramdisk: a helper program for smf_root_is_ramdisk() in
+ * "/lib/svc/share/smf_include.sh".  Exits zero if the root file system is
+ * mounted from a ramdisk, or non-zero if not, or if we hit an error condition.
+ */
+
+#include <stdlib.h>
+#include <stdio.h>
+#include <stdbool.h>
+#include <fcntl.h>
+#include <err.h>
+#include <limits.h>
+#include <string.h>
+#include <sys/modctl.h>
+#include <sys/types.h>
+#include <sys/mkdev.h>
+#include <sys/stat.h>
+
+#define	EXIT_USAGE			2
+#define	EXIT_NOT_RAMDISK		3
+
+bool g_verbose = false;
+
+static bool
+root_is_ramdisk(void)
+{
+	struct stat st;
+	major_t maj;
+	char driver[PATH_MAX + 1];
+
+	if (stat("/", &st) != 0) {
+		err(EXIT_FAILURE, "stat");
+	}
+
+	maj = major(st.st_dev);
+	if (g_verbose) {
+		fprintf(stderr, "major = %lu\n", (long unsigned)maj);
+	}
+
+	if (modctl(MODGETNAME, driver, sizeof (driver), &maj) != 0) {
+		err(EXIT_FAILURE, "modctl");
+	}
+
+	if (g_verbose) {
+		fprintf(stderr, "driver = %s\n", driver);
+	}
+
+	return (strcmp(driver, "ramdisk") == 0);
+}
+
+int
+main(int argc, char *argv[])
+{
+	int c;
+
+	while ((c = getopt(argc, argv, ":v")) != -1) {
+		switch (c) {
+		case 'v':
+			g_verbose = true;
+			break;
+		case ':':
+			errx(EXIT_USAGE, "-%c requires an operand", optopt);
+			break;
+		case '?':
+			errx(EXIT_USAGE, "-%c unknown", optopt);
+			break;
+		}
+	}
+
+	return (root_is_ramdisk() ? EXIT_SUCCESS : EXIT_NOT_RAMDISK);
+}