My teacher gives me a linux kernel vmlinuz-3.17.2 and a rootfs.ext2 which can be loaded to qemu. And he asks me to build a simplest kernel module which prints a hello world as homework.
- Firstly, I download the kernel source and run make oldconfig
- Secondly, I make the config to be PREEMPT and without modversions (according to uname -a of vmlinuz running in qemu) , then make prepare
- Thirdly, I compile the kernel mod and copy hello.ko in rootfs.ext2
- Finally, In qemu, I run insmod hello.ko which exit without any prompt and echo $? returns 0.
However, I can't see anything in dmesg or /var/log/messages Is there anything wrong? How can I do with this? There is also nothing to be printed when I run rmmod hello.ko successfully.
My log level is 7 4 1 7
I have make my hello.c as follows:
#include <linux/init.h>
#include <linux/module.h>
static int __init hello_init(void)
{
pr_info("Hello World");
return -1;
// I changed this to -1 deliberately, Because It seems that the code is not executed.
}
static void __exit hello_exit(void)
{
printk(KERN_ERR "Goodbye, cruel world\n");
}
MODULE_LICENSE("GPL");
module_init(hello_init);
module_exit(hello_exit);
