内核模块编程初探

作者：童燕群 | 发布日期：九月 8, 2012 | 阅读次数（3,055） | 评论 |

微信扫描，分享到朋友圈和群

照着这里的简单教程（http://www.kerneltravel.net/?page_id=8）编写了第一个内核模块，对中断和内核模块注册形成了简单的认识。

Makefile文件：

# Makefile2.6
obj-m += first.o       
CURRENT_PATH := $(shell pwd) 
LINUX_KERNEL := $(shell uname -r)
LINUX_KERNEL_PATH := /usr/src/kernels/$(LINUX_KERNEL) 
all:
    make -C $(LINUX_KERNEL_PATH) M=$(CURRENT_PATH) modules   
clean:
    make -C $(LINUX_KERNEL_PATH) M=$(CURRENT_PATH) clean

模块代码：

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

static int irq;
static char *interface;

module_param(irq, int, 0644);
module_param(interface, charp, 0644);

static irqreturn_t specialirq(int irq, void *dev_id/*, struct pt_regs *regs*/)
{
  static int mycount = 0;
  printk("irq: %d occured on device: %d!\n", irq, *(int*)dev_id);
  mycount++;
  return IRQ_NONE;
}

static int __init specialirq_init(void)
{
  printk ("begin to init my firt module!\n");
  if (request_irq(irq, &specialirq, IRQF_SHARED,interface, &irq)) 
  {
    printk(KERN_ERR "specialirq: cannot register IRQ %d.\n", irq);
    return -EIO;
  }
  printk("registe callback on %s of IRQ %d successfully!\n", interface, irq);
  printk("end to init my first module!\n");
  return 0;
}

static void __exit specialirq_exit(void)
{
  printk("begin to unloading my first module.\n");
  free_irq(irq, &irq);
  printk("end to unloading my firt module.\n");
  return;
}

module_init(specialirq_init);
module_exit(specialirq_exit);
MODULE_LICENSE("GPL");

每个内核模块都有一个init方法和exit方法。

在init方法中，根据输入参数注册一个设备中断的回调函数：

如，注册中断响应模块之前的系统中断信息如下：

cat /proc/interrupts 
           CPU0       CPU1       
  0:        271          0   IO-APIC-edge      timer
  1:        453          1   IO-APIC-edge      i8042
  3:          0          1   IO-APIC-edge    
  4:          0          1   IO-APIC-edge    
  6:          2          3   IO-APIC-edge      floppy
  7:          0          0   IO-APIC-edge      parport0
  8:          1          0   IO-APIC-edge      rtc0
  9:          0          0   IO-APIC-fasteoi   acpi
 12:      10534          2   IO-APIC-edge      i8042
 14:          0          0   IO-APIC-edge      ata_piix
 15:      12006          1   IO-APIC-edge      ata_piix
 16:       1505          0   IO-APIC-fasteoi   vmci, Ensoniq AudioPCI
 17:      27704       1008   IO-APIC-fasteoi   ehci_hcd:usb1, BusLogic BT-958
 18:          0          0   IO-APIC-fasteoi   uhci_hcd:usb2
 19:      42037         42   IO-APIC-fasteoi   vmxnet ether
NMI:          0          0   Non-maskable interrupts
LOC:     394468     383646   Local timer interrupts
RES:      32430      46661   Rescheduling interrupts
CAL:        247        186   function call interrupts
TLB:       3181       3149   TLB shootdowns
TRM:          0          0   Thermal event interrupts
SPU:          0          0   Spurious interrupts
ERR:          0
MIS:          0

执行：insmod first.ko interface=eth0 irq=19

表示注册eth0设备的19号中断的响应程序。当eth0发出19号中断时，specialirq方法会被回调。

注册后系统的中断信息如下：

cat /proc/interrupts 
           CPU0       CPU1       
  0:        271          0   IO-APIC-edge      timer
  1:        453          1   IO-APIC-edge      i8042
  3:          0          1   IO-APIC-edge    
  4:          0          1   IO-APIC-edge    
  6:          2          3   IO-APIC-edge      floppy
  7:          0          0   IO-APIC-edge      parport0
  8:          1          0   IO-APIC-edge      rtc0
  9:          0          0   IO-APIC-fasteoi   acpi
 12:      10534          2   IO-APIC-edge      i8042
 14:          0          0   IO-APIC-edge      ata_piix
 15:      12174          1   IO-APIC-edge      ata_piix
 16:       1505          0   IO-APIC-fasteoi   vmci, Ensoniq AudioPCI
 17:      27745       1008   IO-APIC-fasteoi   ehci_hcd:usb1, BusLogic BT-958
 18:          0          0   IO-APIC-fasteoi   uhci_hcd:usb2
 19:      42632         42   IO-APIC-fasteoi   vmxnet ether, eth0
NMI:          0          0   Non-maskable interrupts
LOC:     397939     386623   Local timer interrupts
RES:      32784      47155   Rescheduling interrupts
CAL:        247        188   function call interrupts
TLB:       3201       3180   TLB shootdowns
TRM:          0          0   Thermal event interrupts
SPU:          0          0   Spurious interrupts
ERR:          0
MIS:          0