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0024_Kernel_Modules.md

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Kernel Modules

参考文档

install kernel headers

  • sudo apt-get install raspberrypi-kernel-headers 
    root@raspberrypi:~# ls /lib/modules/$(uname -r)/build -al
lrwxrwxrwx 1 root root 35 Jul  9 15:07 /lib/modules/4.19.57-v7l+/build -> /usr/src/linux-headers-4.19.57-v7l+

build kernel module

  • hello.c 
    #include <linux/init.h>
#include <linux/kernel.h>
#include <linux/module.h>

MODULE_LICENSE("GPL");
MODULE_DESCRIPTION("Do-nothing test driver");
MODULE_VERSION("0.1");

static int __init hello_init(void){
   printk(KERN_INFO "Hello, world.\n");
   return 0;
}

static void __exit hello_exit(void){
   printk(KERN_INFO "Goodbye, world.\n");
}

module_init(hello_init);
module_exit(hello_exit);
  • Makefile 
    obj-m += hello.o

all:
        make -C /lib/modules/$(shell uname -r)/build M=$(PWD) modules

clean:
        make -C /lib/modules/$(shell uname -r)/build M=$(PWD) clean

modules_install: all
        $(MAKE) -C $(KERNEL_SRC) M=$(SRC) modules_install
        $(DEPMOD)
  • make log 
    pi@raspberrypi:~/zengjf/hello $ make
make -C /lib/modules/4.19.57-v7l+/build M=/home/pi/zengjf/hello modules
make[1]: Entering directory '/usr/src/linux-headers-4.19.57-v7l+'
  CC [M]  /home/pi/zengjf/hello/hello.o
  Building modules, stage 2.
  MODPOST 1 modules
  CC      /home/pi/zengjf/hello/hello.mod.o
  LD [M]  /home/pi/zengjf/hello/hello.ko
make[1]: Leaving directory '/usr/src/linux-headers-4.19.57-v7l+'
pi@raspberrypi:~/zengjf/hello $ ls
hello.c  hello.ko  hello.mod.c  hello.mod.o  hello.o  Makefile  modules.order  Module.symvers
  • hello_module source code branch
  • dmesg查看log输出；
  • sudo cp hello.ko /lib/modules/4.19.57-v7l+/kernel/
  • depmod -a
  • cat /lib/modules/4.19.57-v7l+/modules.order 
    kernel/arch/arm/crypto/aes-arm.ko
kernel/arch/arm/crypto/aes-arm-bs.ko
kernel/arch/arm/crypto/sha1-arm.ko
[...省略]
kernel/lib/ts_bm.ko
kernel/lib/ts_fsm.ko
kernel/lib/lru_cache.ko
hello.ko
  • modprobe hello
  • cat /etc/modules 
    # /etc/modules: kernel modules to load at boot time.
#
# This file contains the names of kernel modules that should be loaded
# at boot time, one per line. Lines beginning with "#" are ignored.

i2c-dev
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