[SOLVED] Kernel module source file after preprocessing

Issue

Let we've written the following simplest module source file:

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

static int __init md_init(void){
    printk("Hello kernel");
    return 0;
}

static void __exit md_exit(void){
    printk("Goodbye kernel");
}

module_init(md_init);
module_exit(md_exit);

How can I see this source after preprocessing? I want to know how are __init and __exit macros deployed and what's the module_init(md_init) and module_exit(md_exit)? How it works?

Solution

If you only plan to get the preprocessed output of kernel module, don't use Makefile, cause Makefiles (sub-make) will try to produce an object file with ability to insert into the kernel. Which contradicts with gcc -E, which just stops after preprocessing. So, just do the followings by using gcc:

  gcc -E new.c -I$TREE/include -I$TREE/arch/x86/include -I$TREE/include/uapi

-E is to get the preprocessed output, $TREE is the location of your kernel tree and if you use other arch then change x86. And we know that, gcc takes include dir parameter with -I, so pass all the kernel include dir through -I. Hope this helps!

Answered By - rakib_

Answer Checked By - Marie Seifert (WPSolving Admin)