接上一篇 写一个 Linux内核 hello world 模块, 这次我们写2个内核模块 hello & world, 并且 world 模块依赖于 hello 模块.

hello 模块

源代码: hello.c

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

static int __init hello_init(void)
{
        pr_info("hello module is loaded\n");
        return 0;
}

static void __exit hello_exit(void)
{
        pr_info("hello module is unloaded\n");
}

void say_hello(void)
{
        pr_info("hello ");
}

EXPORT_SYMBOL(say_hello);

module_init(hello_init);
module_exit(hello_exit);
MODULE_LICENSE("free");

world 模块

源代码: world.c

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

void say_hello(void);

static int __init world_init(void)
{
        pr_info("world module is loaded\n");
    say_hello();
        pr_info("world\n");
        return 0;
}

static void __exit world_exit(void)
{
        pr_info("world module is unloaded\n");
}

module_init(world_init);
module_exit(world_exit);
MODULE_LICENSE("free");

Makefile

源代码: Makefile. 缩进使用 tab.

obj-m := world.o hello.o

KDIR := /lib/modules/`uname -r`/build/
PWD := $(shell pwd)

default:
    $(MAKE) -C $(KDIR) M=$(PWD) modules

clean:
    $(MAKE) -C $(KDIR) M=$(PWD) clean

编译模块

$ make
make -C /lib/modules/`uname -r`/build/ M=/home/supra/work/modules/deps modules
make[1]: Entering directory '/home/supra/work/jammy/jammy-Ubuntu-5.15.0-70.77-test'
  CC [M]  /home/supra/work/modules/deps/world.o
  CC [M]  /home/supra/work/modules/deps/hello.o
  MODPOST /home/supra/work/modules/deps/Module.symvers
  CC [M]  /home/supra/work/modules/deps/hello.mod.o
  LD [M]  /home/supra/work/modules/deps/hello.ko
  BTF [M] /home/supra/work/modules/deps/hello.ko
  CC [M]  /home/supra/work/modules/deps/world.mod.o
  LD [M]  /home/supra/work/modules/deps/world.ko
  BTF [M] /home/supra/work/modules/deps/world.ko
make[1]: Leaving directory '/home/supra/work/jammy/jammy-Ubuntu-5.15.0-70.77-test'

加载模块

$ sudo insmod hello.ko

$ tail -n 1  /var/log/syslog
Jul 10 14:15:22 supra kernel: [ 3313.748762] hello module is loaded

$ sudo cat /proc/modules | grep hello
hello 16384 0 - Live 0xffffffffc0797000 (POE)

$ sudo insmod world.ko

$ tail -n 3 /var/log/syslog
Jul 10 14:19:22 supra kernel: [ 3553.077383] world module is loaded
Jul 10 14:19:22 supra kernel: [ 3553.077385] hello
Jul 10 14:19:22 supra kernel: [ 3553.077386] world

$ sudo cat /proc/modules | grep hello
hello 16384 1 world, Live 0xffffffffc0797000 (POE)

查看模块依赖

$ lsmod | grep hello
hello                  16384  1 world

$ lsmod | grep world
world                  16384  0
hello                  16384  1 world

相反顺序卸载模块

$ sudo rmmod world.ko
$ sudo rmmod hello.ko

$ tail -n 2 /var/log/syslog
Jul 10 14:26:00 supra kernel: [ 3949.339943] world module is unloaded
Jul 10 14:26:05 supra kernel: [ 3954.185122] hello module is unloaded