mod_hello/mod_hello.c

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

#include <linux/sched.h>

#include <linux/kallsyms.h> 
#include <linux/string.h>

#include <linux/fs.h>
#include <linux/miscdevice.h>

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

static long
hello_control_ioctl(struct file *file, unsigned int cmd, unsigned long arg)
{
    //int ret = -ENOTTY;

    //switch (cmd) {
    //}
    printk(KERN_INFO "[%s] received command: %d\n", __this_module.name, cmd);
    return 0;
}

static const struct file_operations hello_ctl_fops = {
    .unlocked_ioctl = hello_control_ioctl,
    .compat_ioctl   = hello_control_ioctl,
    .owner          = THIS_MODULE,
    .llseek         = noop_llseek,
};

static struct miscdevice hello_misc = {
    .minor          = MISC_DYNAMIC_MINOR,
    .name           = "helloctl",
    .fops           = &hello_ctl_fops,
};

MODULE_ALIAS_MISCDEV(MISC_DYNAMIC_MINOR);
MODULE_ALIAS("devname:helloctl");

//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)
{
    printk(KERN_INFO "[%s] module loaded.\n", __this_module.name);
    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;
}


// module parameters
static char *sym_name = "files";
module_param(sym_name, charp, S_IRUGO);

static void hello_fib_stuff(long f_cap, long f_start1, long f_start2) {
    long f_int;
    unsigned long jiffies_start, jiffies_diff;

    jiffies_start = jiffies;
    f_int = hello_fib(f_cap, f_start1, f_start2);

    jiffies_diff = jiffies - jiffies_start;
    printk("[%s] fib of %ld and %ld (up to %ld): %ld (in only %lu jiffies)\n",
            __this_module.name, f_start1, f_start2, f_cap, f_int, jiffies_diff);
}

#define FILENAME_LENGTH 255

static int __init hello_init(void)
{
    char filename[FILENAME_LENGTH];
    unsigned long sym_addr;

    // in linux/sched.h
    //struct task_struct *current;
    printk(KERN_INFO "[%s] pid: %d, comm: %s\n", __this_module.name, current->pid, current->comm);

    hello_print_hello();

    printk(KERN_INFO "[%s] looking up '%s'\n", __this_module.name, sym_name);
    sym_addr = kallsyms_lookup_name(sym_name);
    printk(KERN_INFO "[%s] %s 0x%lx\n", __this_module.name, sym_name, sym_addr);

    if ((char *)sym_addr != NULL) {
        strncpy(filename, (char *)sym_addr, FILENAME_LENGTH);
        printk(KERN_INFO "[%s] %s (0x%lx): %s\n", __this_module.name, sym_name, sym_addr, filename);
    }

    hello_fib_stuff(10000000, 0, 1);
    
    return misc_register(&hello_misc);
}

static void __exit hello_cleanup(void)
{
    if (misc_deregister(&hello_misc) < 0) {
        printk(KERN_INFO "[%s] misc_deregister failed for control device.\n", __this_module.name);
    }
    printk(KERN_INFO "[%s] module unloaded.\n", __this_module.name);
}

module_init(hello_init);
module_exit(hello_cleanup);

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