Hello World for Kernel Development

[lachjames]

Hi :) I'm fairly new to the world of kernel module development, and I'm hoping to get a bit of guidance - I think I've got the kernel modules compiling, installed, and in use, but I don't know how to confirm this. Some kind of "hello world" would be nice - even just a way to print a message to dmesg to let me know that it's applying my code.

I've tried a few things (nv_log, dpPrint, DP_LOG) but nothing seems to work. I also tried setting an appropriate keyword filter using RmMsg and compiling with make modules -j$(nproc) DEBUG=1 - the latter doesn't seem to have had an effect, and the former just spams a bunch of stuff to dmesg so I'm not sure if what I'm printing is there or not (grep can't find it but perhaps it's just being deleted by later calls?)

I'd appreciate some guidance, and apologies if these are trivial questions - I'm very eager to learn :)

[ghost]

Hello! Welcome to the world of kernel module development. Don't worry; we all start somewhere, and I'm here to help.

To print messages to the kernel log (dmesg), you can use the printk function in your kernel module code. Here's a simple "hello world" example:

#include <linux/module.h>
#include <linux/kernel.h>

MODULE_LICENSE("GPL");
MODULE_AUTHOR("Your Name");
MODULE_DESCRIPTION("A simple kernel module");
MODULE_VERSION("0.1");

static int __init hello_init(void) {
    printk(KERN_INFO "Hello, world!\n");
    return 0;
}

static void __exit hello_exit(void) {
    printk(KERN_INFO "Goodbye, world!\n");
}

module_init(hello_init);
module_exit(hello_exit);

Make sure you compile your module with debugging enabled. You can add EXTRA_CFLAGS=-g to your Makefile to achieve this. Then, build and install the module:

make -C /path/to/kernel/source M=$(pwd) modules
sudo insmod your_module.ko

You can check if your module is loaded and see its output in dmesg:

lsmod | grep your_module
dmesg | grep "Hello, world!"

This should help you confirm if your module is being applied and printing messages as expected.

If you encounter any issues or have more questions, feel free to ask. Happy learning! :)

[zulloper]

what is nv_log binary?!