Kernel module compilation errors

[greg@kroah.com (Greg KH)]

On Thu, Aug 11, 2016 at 07:25:45PM +0000, Matt M wrote:
> I am just getting started with kernel module development, and I can't get
> anything to compile.
> 
> I get the following errors:
> 
> In file included from main.c:1:0:
> /usr/src/linux/include/linux/init.h:142:13: error: expected ?=?, ?,?, ?;?,
> ?asm? or ?__attribute__? before ?load_default_modules?
> ?void __init load_default_modules(void);
> ? ? ? ? ? ? ?^~~~~~~~~~~~~~~~~~~~
> /usr/src/linux/include/linux/init.h:143:12: error: expected ?=?, ?,?, ?;?,
> ?asm? or ?__attribute__? before ?init_rootfs?
> ?int __init init_rootfs(void);
> ? ? ? ? ? ? ^~~~~~~~~~~
> /usr/src/linux/include/linux/init.h:285:13: error: expected ?=?, ?,?, ?;?,
> ?asm? or ?__attribute__? before ?parse_early_param?
> ?void __init parse_early_param(void);
> ? ? ? ? ? ? ?^~~~~~~~~~~~~~~~~
> /usr/src/linux/include/linux/init.h:286:13: error: expected ?=?, ?,?, ?;?,
> ?asm? or ?__attribute__? before ?parse_early_options?
> ?void __init parse_early_options(char *cmdline);
> 
> 
> The errors go on and on, but the majority look like that.
> 
> My code:
> 
> #include <linux/init.h>
> #include <linux/module.h>
> 
> int main() {
> return 0;
> }
> 
> 
> The compile command:
> gcc -I /usr/src/linux/include/ main.c

That's not how you compile a Linux kernel module, sorry.

Please read the very good documentation for how to set up a Makefile for
building a kernel module.  It's in the kernel's Documentation/
directory.

best of luck,

greg k-h