/*
 * 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);
}