linux_test_for_realtime_kernel1.c - simple test whether the current Linux kernel is a realtime kernel
Posted by Anonymous on Mon 6th Mar 2023 13:04
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/*
 * linux_test_for_realtime_kernel1.c - simple test whether the
 * current Linux kernel is a realtime kernel
 *
 * Written by Roland Mainz <roland.mainz@nrubsig.org>
 */

#include <stdlib.h>
#include <stdbool.h>
#include <stdio.h>
#include <fcntl.h>
#include <unistd.h>
#include <errno.h>
#include <string.h>

/*
 * EINTR_REPEAT - make sure we repeat aborted syscalls since
 * we cannot rely on |SA_RESTART| in library code
 */
#define EINTR_REPEAT(expr) \
        { while((expr) && (errno == EINTR)) errno=0; };

int linux_is_realtime_kernel(void)
{
        int     fd;
        /*
         * Lazy buffer sizing. Instead of |fstat()| on fd or
         * loop on |read()| we just assume that the contents
         * of "/proc/sys/kernel/version" have always a size
         * less than 1k.
         */
        char    buff[1024];
        ssize_t s;
        int     res = 0;

        EINTR_REPEAT(fd = open("/proc/sys/kernel/version",
                O_RDONLY|O_CLOEXEC));
        if (fd == -1) {
                perror("Cannot open /proc/sys/kernel/version");
                return -1;
        }

        EINTR_REPEAT(s = read(fd, buff, sizeof(buff)-1));

        if (s > 0) {
                buff[s] = '\0';
                if (strstr(buff, "PREEMPT_RT"))
                        res = 1;
        }

        (void)close(fd);

        return res;
}

int main(int ac, char *av[])
{
        int x;

        (void)puts("#start.");

        x = linux_is_realtime_kernel();
        (void)printf("kernel a realtime-kernel = %d\n", x);

        (void)puts("#done.");

        return EXIT_SUCCESS;
}