Linux内核模块编程的编译错误

Question

I am learning Linux kernel module programming. I am using Beaglebone black for that. I have made simple 'Hello World' application and makefile. I have checked my makefile it's proper. But when I command 'make', it gives me following error:

root@beaglebone:/home/sonu# make
make: Warning: File `Makefile' has modification time 2.2e+02 s in the future
make -C /lib/modules/3.8.13-bone70/build M=/home/sonu modules
make: *** /lib/modules/3.8.13-bone70/build: No such file or directory.  Stop.
make: *** [all] Error 2

Though I referred some websites. But, all they are asking me to install packages. As I am a newbie. I don't even know how to configure and start internet connection on Beaglebone using ethernet. Please help me I am stuck. Thanks in advance.

Code is:

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

static int __init hello(void)
{
   printk(KERN_INFO "Hello World!");
   return 0;
}

static void __exit hello_cleanup(void)
{
   printk(KERN_INFO "Bye");
}

module_init(hello);
module_exit(hello_cleanup);

Makefile is:

obj-m+=Hello.o

all:
        make -C /lib/modules/$(shell uname -r)/build M=$(PWD) modules
        $(CC) Hello.c -o test
clean:
        make -C /lib/modules/$(shell uname -r)/build M=$(PWD) clean
        rm test

Answer 1

It appears that you're trying to build your module for a kernel version that you haven't installed the headers for.

Instead of calling uname directly in your rules, it's helpful to put that into a variable you can override:

obj-m+=Hello.o

KSRC := /lib/modules/$(shell uname -r)/build

all:
        make -C $(KSRC) M=$(PWD) modules
        $(CC) Hello.c -o test
clean:
        make -C $(KSRC) M=$(PWD) clean
        rm test

Now, you can override with the actual location of your kernel headers:

make KSRC=/usr/src/linux-headers-4.9.2 all

You can simplify the Makefile further with a catch-all rule:

obj-m+=Hello.o

KSRC := /lib/modules/$(shell uname -r)/build

all: modules
        $(CC) Hello.c -o test

%:
        make -C $(KSRC) M=$(PWD) $@

clean::
        make -C $(KSRC) M=$(PWD) clean
        $(RM) test