Designing BSD Rootkits

"Hello, world!"

You now know enough to write your first KLD. Listing 1-1 is a complete "Hello, world!" module.

#include <sys/param.h>
#include <sys/module.h>
#include <sys/kernel.h>
#include <sys/systm.h>

/* The function called at load/unload. */
static int
load(struct module *module, int cmd, void *arg)
{
        int error = 0;

        switch (cmd) {
        case MOD_LOAD:
                uprintf("Hello, world!\n");
                break;

        case MOD_UNLOAD:
                uprintf("Good-bye, cruel world!\n");
                break;

        default:
                error = EOPNOTSUPP;
                break;
        }

        return(error);

}

/* The second argument of DECLARE_MODULE. */
static moduledata_t hello_mod = {
        "hello",        /* module name */
        load,           /* event handler */
        NULL            /* extra data */

};

DECLARE_MODULE(hello, hello_mod, SI_SUB_DRIVERS, SI_ORDER_MIDDLE);

Listing 1-1: hello.c

As you ...