Escrevendo seu primeiro módulo de kernel (Linux)

1. Escreva seu primeiro
MÓDULO DE
KERNEL
(LINUX)

2. Em quatro atos
●
Hello World!
●
Character driver
●
Miscellaneous driver
●
Ramdisk

3. 0 – Hello World
●
Olá mundo!
●
Diego Ramos Ruggeri
●
http://vai.la/62u3

4. 0 – Hello World
●
Linux é monolítico
●
Módulos carregados em tempo de
execução
●
Ciclo de vida
●
Básico: Inicializar e Limpar

5. 0 – Hello World
Porque?
●
Hardware livre
●
Entender o Linux
●
OOP em C
●
Projeto de software livre

6. static int __init hello_module(void)
{
printk(KERN_INFO "Hello World!n");
return 0;
}
static void __exit goodbye_module(void)
{
printk(KERN_INFO "Adiosn");
}
module_init(hello_module);
module_exit(goodbye_module);
MODULE_LICENSE("GPL");
MODULE_AUTHOR("Diego Ruggeri");
MODULE_DESCRIPTION("Hello World module");

7. 0 – Hello World
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

8. 0 – Hello World
●
modinfo
●
insmod
●
lsmod
●
rmmod
●
dmesg

9. 1 – Char Dev
●
ioctls
●
net
●
/dev
●
/sys
●
/dev
●
Block device
●
Character device
●
Major Minor

10. static struct file_operations fops = {
.read = device_read,
.write = device_write,
.open = device_open,
.release = device_release
};
static int __init hello_module(void)
{
major = register_chrdev(0, DEVICE, &fops);
/* … */
}
static void __exit goodbye_module(void)
{
unregister_chrdev(major, DEVICE);
}

11. 2 – Misc Dev
●
mknod /dev/fisl15 c $MAJOR $MINOR
●
udev
●
Miscellaneous API

12. static struct file_operations fops = { /*...*/ };
static struct miscdevice mdev = {
.minor = MISC_DYNAMIC_MINOR,
.name = DEVICE,
.fops = &fops,
};
static int __init hello_module(void)
{
misc_register(&mdev)
/* … */
}
static void __exit goodbye_module(void)
{
misc_deregister(&mdev);
}

13. 3 - Ramdisk
●
Char device +
●
Misc api +
●
Aloca memória (slab) +
●
open, close, read, write

14. static int __init hello_module(void)
{
disk = (char*) kzalloc(DISK_SIZE *
sizeof(char), GFP_KERNEL);
/*…*/
}
static void __exit goodbye_module(void)
{
kfree(disk);
/*...*/
}

15. static ssize_t device_read(struct file *filp, char
*buffer, size_t length,loff_t * offset)
{
/*...*/
copy_to_user(buffer, message, len);
/*...*/
}
static ssize_t device_write(struct file *filp, const
char *buff, size_t len, loff_t * off)
{
copy_from_user(disk, buff, len)
}

16. Obrigado
diego@ruggeri.net.br
http://github.com/diegor2