从用户空间应用程序调用内核空间中的用户定义函数 [英] Calling a user defined function in kernel space from user space application program

问题描述

我已经在设备驱动程序中编写了一个用户定义的函数，我想从用户空间应用程序中调用它.我该如何实现?

I have written a user defined function in my device driver and I want to call it from user space application program. How do I achieve this?

我定义的用户定义函数是内核定义函数以外的任何函数.在struct file_operations中定义的指针，如下所示.

What I mean by user defined function is, any function other than the kernel defined functions. Pointers to which is defined in struct file_operations, as below.

struct file_operations {
       struct module *owner;
       loff_t (*llseek) (struct file *, loff_t, int);
       ssize_t (*read) (struct file *, char *, size_t, loff_t *);
       ssize_t (*write) (struct file *, const char *, size_t, loff_t *);
       int (*readdir) (struct file *, void *, filldir_t);
       unsigned int (*poll) (struct file *, struct poll_table_struct *);
       int (*ioctl) (struct inode *, struct file *, unsigned int, unsigned long);
       int (*mmap) (struct file *, struct vm_area_struct *);
       int (*open) (struct inode *, struct file *);
       int (*flush) (struct file *);
       int (*release) (struct inode *, struct file *);
       int (*fsync) (struct file *, struct dentry *, int datasync);
       int (*fasync) (int, struct file *, int);
       int (*lock) (struct file *, int, struct file_lock *);
         ssize_t (*readv) (struct file *, const struct iovec *, unsigned long,
          loff_t *);
         ssize_t (*writev) (struct file *, const struct iovec *, unsigned long,
          loff_t *);
    };

例如在我的驱动程序中，我具有以下要求，

For eg. in my driver I've the following,

struct file_operations fops = {
.read = my_read,
.write = my_write,
};

，我可以使用调用read和write从用户空间应用程序中调用这些函数.

and I can call these functions from user space application program using the calls read and write.

我在内核源代码中也有一个名为user_defined的函数，我的问题是如何从用户空间程序调用此函数?

I also have a function named user_defined in kernel source and my question is how do I call this from user space program?

推荐答案

好吧，您所拥有的通常称为"syscall".我建议您阅读内核开发人员文档，以了解如何公开一个新的syscall.在用户空间方面，libc为您提供了一个函数syscall，您可以使用它调用内核空间.但是通常您会在其周围写一个包装器.

Well, what you have there is normally referred to as "syscall". I suggest you read into the kernel developer documentation on how to expose a new syscall. On the userspace side, the libc provides you a function syscall, that you can use to call into kernel space. But normally you write a wrapper around it.

但是应避免引入新的系统调用.调用内核空间的首选方法是使用sysfs并将用户空间可调用函数作为其中的文件公开.

However introducing new syscalls should be avoided. The preferred way to call into kernel space is to use sysfs and expose the user space callable functions as files therein.

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