/*
 * 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 (c) 2016 by Delphix. All rights reserved.
 */

/*
 * Steal memory from the kernel, forcing the ARC to decrease in size, and hold
 * it until the process receives a signal.
 */

#include <stdio.h>
#include <sys/types.h>
#include <sys/shm.h>
#include <strings.h>
#include <stdlib.h>
#include <unistd.h>
#include <errno.h>

static void
usage(char *progname)
{
        (void) fprintf(stderr, "Usage: %s -f <bytes>\n", progname);
        exit(1);
}

static void
fail(char *err, int rval)
{
        perror(err);
        exit(rval);
}

static void
daemonize(void)
{
        pid_t   pid;

        if ((pid = fork()) < 0) {
                fail("fork", 1);
        } else if (pid != 0) {
                (void) fprintf(stdout, "%ld\n", pid);
                exit(0);
        }

        (void) setsid();
        (void) close(0);
        (void) close(1);
        (void) close(2);
}

int
main(int argc, char *argv[])
{
        int             c;
        boolean_t       fflag = B_FALSE;
        char            *prog = argv[0];
        long long       size;
        char            *stroll_leftovers;
        int             shm_id;
        void            *shm_attached;

        while ((c = getopt(argc, argv, "f")) != -1) {
                switch (c) {
                /* Run in the foreground */
                case 'f':
                        fflag = B_TRUE;
                        break;
                default:
                        usage(prog);
                }
        }

        argc -= optind;
        argv += optind;

        if (argc != 1)
                usage(prog);
        size = strtoll(argv[0], &stroll_leftovers, 10);
        if (size <= 0)
                fail("invalid size in bytes", 1);

        if ((shm_id = shmget(IPC_PRIVATE, size, IPC_CREAT|IPC_EXCL)) == -1)
                fail("shmget", 1);
        if ((shm_attached = shmat(shm_id, NULL, SHM_SHARE_MMU)) == (void *)-1)
                fail("shmat", 1);

        if (fflag == B_FALSE)
                daemonize();
        (void) pause();

        /* NOTREACHED */
        return (0);
}