adding a simple ioctl to a new /dev/helloctl

mod_hello.c

@@ -6,11 +6,41 @@
 #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";
 
@@ -39,45 +69,54 @@ long hello_fib(long times, long n1, long n2)
 }
 
 
+// module parameters
 static char *sym_name = "files";
 module_param(sym_name, charp, S_IRUGO);
 
-static int __init hello_init(void)
+static void hello_fib_stuff(long f_cap, long f_start1, long f_start2) {
-{
+    long f_int;
-    long f_int, f_cap, f_start1, f_start2;
-    char filename[255];
     unsigned long jiffies_start, jiffies_diff;
-    unsigned long sym_addr;
-
-    // in linux/sched.h
-    //struct task_struct *current;
-    printk("[%s] pid: %d, comm: %s\n", __this_module.name, current->pid, current->comm);
-
-    hello_print_hello();
-
-    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);
-
 
     jiffies_start = jiffies;
-    f_cap = 10000000;
-    f_start1 = 0;
-    f_start2 = 1;
     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);
+}
 
-    return 0;
+#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);
 }