如何给Linux驱动实现信号通知机制？

2025-03-03

send_sig_info是Linux内核中的一个函数，用于向指定进程发送信号。它允许内核代码向特定进程发送信号，并附带一些额外的信息（通过struct siginfo结构体传递）。

实例代码

// simple_cdev.c

#include <linux/cdev.h>
#include <linux/device.h>
#include <linux/device/class.h>
#include <linux/err.h>
#include <linux/errno.h>
#include <linux/fs.h>
#include <linux/init.h>
#include <linux/ioctl.h>
#include <linux/kernel.h>
#include <linux/minmax.h>
#include <linux/module.h>
#include <linux/sched/signal.h>
#include <linux/slab.h>
#include <linux/types.h>
#include <linux/uaccess.h>

#define BUFFER_SIZE 1024
#define DEV_MINOR_COUNTS 1
#define DEV_NAME "simple_cdev"

#define SIGNR 44
#define REGISTER_UAPP _IO('R', 'G')

typedef struct {
    struct cdev *cdev;   // 字符设备
    struct class *class; // 设备类
    struct device *dev;  // /dev目录下的设备

    char buffer[BUFFER_SIZE]; // 缓冲区
} simple_cdev_t;

static simple_cdev_t my_cdev = {0};

static int _open(struct inode *inode, struct file *file) {
    pr_info("simple_cdev_open\n");
    return 0;
}

static int _release(struct inode *inode, struct file *file) {
    pr_info("simple_cdev_release\n");
    return 0;
}

static long int _unlocked_ioctl(struct file *file, unsigned int cmd,
                                unsigned long arg) {
    if (cmd == REGISTER_UAPP) {
        struct task_struct *task = get_current();
        pr_info("current task id = %d", task->pid);

        struct siginfo info = {
            .si_signo = SIGNR,
            .si_code = SI_QUEUE,
        };

        // 发送信号
        int ret = send_sig_info(SIGNR, (struct kernel_siginfo *)&info, task);
        if (ret < 0) {
            pr_err("send_sig_info failed. errno = %d", ret);
            return ret;
        }
    }

    return 0;
}

static struct file_operations fops = {
    .open = _open,
    .unlocked_ioctl = _unlocked_ioctl,
    .release = _release,
};

static int __init simple_cdev_init(void) {
    pr_info("simple_cdev_init\n");

    my_cdev.cdev = cdev_alloc();
    if (!my_cdev.cdev) {
        pr_err("simple_cdev cdev_alloc failed!\n");
        return -ENOMEM;
    }

    // 初始化字符设备
    cdev_init(my_cdev.cdev, &fops);

    // 申请设备号, 由系统分配主设备号和一个从设备号
    int ret =
        alloc_chrdev_region(&my_cdev.cdev->dev, 0, DEV_MINOR_COUNTS, DEV_NAME);
    if (ret) {
        pr_err("simple_cdev alloc_chrdev_region failed!\n");
        return ret;
    }

    pr_info("simple_cdev major = %d\n", MAJOR(my_cdev.cdev->dev));

    // 添加到内核
    ret = cdev_add(my_cdev.cdev, my_cdev.cdev->dev, DEV_MINOR_COUNTS);
    if (ret) {
        pr_err("simple_cdev cdev_add failed!\n");
        return ret;
    }

    // 申请设备类, 会在/sys/class目录下常见一个simple_cdev的目录
    my_cdev.class = class_create("simple_cdev");
    if (IS_ERR(my_cdev.class)) {
        pr_err("simple_cdev class_create failed\n");
        return PTR_ERR(my_cdev.class);
    }

    // 申请设备对象，会在/dev目录下创建设备文件simple_cdev,
    // 并且在/sys/class/simple_cdev目录下常见一个simple_cdev的设备节点
    my_cdev.dev =
        device_create(my_cdev.class, NULL, my_cdev.cdev->dev, NULL, DEV_NAME);
    if (IS_ERR(my_cdev.dev)) {
        pr_err("simple_cdev device_create failed\n");
        return PTR_ERR(my_cdev.dev);
    }

    return 0;
}

static void __exit simple_cdev_exit(void) {
    pr_info("simple_cdev_exit\n");

    device_destroy(my_cdev.class, my_cdev.cdev->dev);
    class_destroy(my_cdev.class);
    cdev_del(my_cdev.cdev);
    unregister_chrdev_region(my_cdev.cdev->dev, DEV_MINOR_COUNTS);
    kfree(my_cdev.cdev);
}

module_init(simple_cdev_init);
module_exit(simple_cdev_exit);

MODULE_LICENSE("GPL");
MODULE_AUTHOR("heng30");
MODULE_VERSION("v0.0.1");
MODULE_DESCRIPTION("A simple_cdev kernel module");

Makefile编译脚本

#!/bin/sh

top-dir = $(shell pwd)
kernel-version = $(shell uname -r)
kernel-dir ?= /lib/modules/$(kernel-version)/build

obj-m += simple_cdev.o

all:
        make -C $(kernel-dir) modules M=$(top-dir)

clean:
        rm -f *.o *.ko *.mod *.mod.c *.order *.symvers
        make -C $(kernel-dir) clean m=$(top-dir)

signal客户端程序

// signal.c
// 编译：gcc -o signal signal.c

#include <assert.h>
#include <fcntl.h>
#include <signal.h>
#include <stdbool.h>
#include <stdio.h>
#include <stdlib.h>
#include <sys/ioctl.h>
#include <unistd.h>

#define SIGTX 44
#define REGISTER_UAPP _IO('R', 'G')

void signal_handler(int sig) { printf("sig = %d\n", sig); }

int main(int argc, char *argv[]) {
    signal(SIGTX, signal_handler);

    int fd = open(argv[1], O_RDONLY);
    assert(fd >= 0);

    printf("pid = %d\n", getpid());

    if (ioctl(fd, REGISTER_UAPP, NULL)) {
        perror("ioctl error");
        close(fd);
        return -1;
    }

    sleep(3);
    close(fd);
    return 0;
}

测试

安装驱动：insmod simple_cdev.ko
移除驱动：rmmod simple_cdev.ko
运行signal /dev/simple_cdev。会输出sig = 44的字符串，表示客户端的信号处理函数被正确的调用了。

Linux驱动