mod_hello/mod_hello.c

#include <linux/module.h>   /* all kernel modules need this */
#include <linux/init.h>     /* provides initialization routines */

#include <linux/kallsyms.h> 

static char __initdata hello_hellomsg[] = KERN_NOTICE "Hello, Kernel, I'm in\n";
static char __exitdata hello_byemsg[] = KERN_NOTICE "Bye, I'm out\n";

static int hello_print_hello(void)
{
    unsigned long i;
    char *symbol_name;

    printk(hello_hellomsg);

    symbol_name = "free_pages";
    printk("looking up '%s'\n", symbol_name);
    i = kallsyms_lookup_name(symbol_name);
    printk("%s 0x%lx\n", symbol_name, i);

    return 0;
}

long hello_fib(long times, long n1, long n2)
{
    long i = 0;
    long prev = n1;
    long curr = n2;
    long next = 0;

    while (i < times)
    {
        next = (prev + curr);
        prev = curr;
        curr = next;
        i++;
    }

    return next;
}

static int __init start_hello_world(void)
{
    long f_int, f_cap, f_start1, f_start2;

    MODULE_LICENSE("GPL");
    MODULE_AUTHOR("Vincent Batts <vbatts@hashbangbash.com>");
    MODULE_DESCRIPTION("just getting familiar");
    MODULE_VERSION("1.0");
    hello_print_hello();

    f_cap = 10000000;
    f_start1 = 0;
    f_start2 = 1;
    f_int = hello_fib(f_cap, f_start1, f_start2);

    printk("fib of %ld and %ld (up to %ld): %ld\n", f_start1, f_start2, f_cap, f_int);
    
    return 0;
}

static void __exit hello_go_away(void)
{
    printk(hello_byemsg);
}

module_init(start_hello_world);
module_exit(hello_go_away);

// vim:set shiftwidth=4 softtabstop=4 expandtab: