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> 
#include <linux/string.h>

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

//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;
}

static int __init hello_init(void)
{
    long f_int, f_cap, f_start1, f_start2;
    unsigned long sym_addr;
    char *sym_name;
    char filename[255];

    hello_print_hello();

    sym_name = "files";
    printk("looking up '%s'\n", sym_name);
    sym_addr = kallsyms_lookup_name(sym_name);
    printk("%s 0x%lx\n", sym_name, sym_addr);

    strncpy(filename, (char *)sym_addr, 255);
    printk(KERN_INFO "[%s] %s (0x%lx): %s\n", __this_module.name, sym_name, sym_addr, filename);


    printk("[%s] jiffies: %lu\n", __this_module.name, jiffies);
    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);
    printk("[%s] jiffies: %lu\n", __this_module.name, jiffies);
    
    return 0;
}

static void __exit hello_cleanup(void)
{
    printk(KERN_INFO "[%s] module unloaded.\n", __this_module.name);
}

module_init(hello_init);
module_exit(hello_cleanup);

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