linux - How do we compile kernel code in C? -

i new c , linux. trying compile below code gives fatal error while compiling. on fixing appreciated.

here code measurecpu.c:

#include <linux/module.h>       #include <linux/kernel.h>       #include <linux/init.h>          #include <linux/hardirq.h> #include <linux/preempt.h> #include <linux/sched.h> #include<stdio.h>  int main() {  uint64_t start, end; int i=0; asm volatile ("cpuid \ n \ t" "rdtsc \ n \ t" "mov %%edx, %0 \ n \ t" "mov %%eax, %1 \ n \ t": "=r" (cycles_high), "=r" (cycles_low)::  "%rax", "%rbx", "%rcx", "%rdx");  for(i=0; i<200000;i++) {}  asm volatile ("rdtscp \ n \ t" "mov %%edx, %0 \ n \ t" "mov %%eax, %1 \ n \ t" "cpuid \ n \ t": "=r" (cycles_high1), "=r" (cycles_low1)::  "%rax", "%rbx", "%rcx", "%rdx");   start = ( ((uint64_t)cycles_high << 32) | cycles_low );  end = ( ((uint64_t)cycles_high1 << 32) | cycles_low1 ); printk(kern_info " \ n function execution time %llu clock cycles",(end - start));  } 

i trying compile way:

gcc -c -o2 -w -wall -isystem /lib/modules/'uname -r'/build/include -d_kernel_ -dmodule measurecpu.c 

i error:

measurecpu.c:1:32: fatal error: linux/module.h: no such file or directory  #include <linux/module.h>                                       ^ compilation terminated. 

i trying compile way gcc -c -o2 -w -wall -isystem /lib/modules/'uname -r'/build/include -d_kernel_ -dmodule measurecpu.c

usually way compile kernel module use kernel build system - ie use make instead of gcc directly. need create makefile , specify object, line obj-m := measurecpu.o in case. after in same directory, issue make command, yield kernel object file measurecpu.ko

# if kernelrelease defined, we've been invoked # kernel build system , can use language. ifneq ($(kernelrelease),)     obj-m := measurecpu.o  # otherwise called directly command # line; invoke kernel build system. else     kerneldir ?= /lib/modules/$(shell uname -r)/build     pwd := $(shell pwd)  default:     $(make) -c $(kerneldir) m=$(pwd) modules  clean:     $(make) -c $(kerneldir) m=$(pwd) modules clean  endif 

note kernel module not user space program, cannot just run it. need tell kernel kernel module via insmod, , check results via dmesg.