将设备驱动程序编译到内核

Question

I'm trying to compile a device driver, but i get the following error, and the same one for all following header

ddd@ddd:~/Desktop$ make
make -C /lib/modules/4.13.0-19-generic/build  M=/home/ddd/Desktop  modules 
make[1]: Entering directory '/usr/src/linux-headers-4.13.0-19-generic'
  CC [M]  /home/ddd/Desktop/message_slot.o
/home/ddd/Desktop/message_slot.c:23:10: fatal error: stdio.h: No such file or directory
 #include <stdio.h>
          ^~~~~~~~~
compilation terminated.
scripts/Makefile.build:309: recipe for target '/home/ddd/Desktop/message_slot.o' failed
make[2]: *** [/home/ddd/Desktop/message_slot.o] Error 1
Makefile:1546: recipe for target '_module_/home/ddd/Desktop' failed
make[1]: *** [_module_/home/ddd/Desktop] Error 2
make[1]: Leaving directory '/usr/src/linux-headers-4.13.0-19-generic'
Makefile:5: recipe for target 'all' failed
make: *** [all] Error 2
ddd@ddd:~/Desktop$ 

I compiler the program using the following makefile:

obj-m := message_slot.o 
KDIR := /lib/modules/$(shell uname -r)/build 
PWD := $(shell pwd) 
all: 
    $(MAKE) -C $(KDIR) M=$(PWD) modules 
clean: 
    $(MAKE) -C $(KDIR) M=$(PWD) clean

The thing is, that by running the small .c code:

#include <stdio.h>
#include <stdli.h>

int main(){
  printf("test");
 }

with the command
gcc test.c -o test
everything compiles. I suspect it's something with the kernel headers, but i've downloaded all headers as specified. I'm running lubuntu 17.10
am i missing something?
Thanks a lot

Answer 1

stdio.h is user space header file not kernel space, that's why your make fails. In driver program why we are including all headers because bcz its not having main() function, Right ?

when you will do make , observe your makefile

 obj-m := message_slot.o 
 KDIR := /lib/modules/$(shell uname -r)/build 

that means you are compiling as a modules and your source code will be in /usr/src/linux-4 (some version).

for eg

   #include <linux/stat.h> 

not

#include <stat.h>

and

xyz@xyz-PC:/usr/src/linux-4.1.39/include/linux$ ls -l stdio.h  
        ls: cannot access stdio.h: No such file or directory

In your driver program why are you including stdio.h because you are not going to use printf, instead printk() ?

Yes in application program you can include stdio.h because you compiling using gcc compiler as a file not as a module .

I hope it helps.