linux内核模块读写文件

#include <linux/module.h>
#include <linux/kernel.h>
#include <linux/fs.h>
#include <linux/uaccess.h>
#include <linux/slab.h>

static char *filename = "/etc/passwd";

static int __init my_module_init(void) {
    struct file *file;
    char buf[128];
    mm_segment_t old_fs;
    loff_t pos = 0;

    file = filp_open(filename, O_RDONLY, 0);
    if (IS_ERR(file)) {
        printk(KERN_ERR "Failed to open file %s\n", filename);
        return PTR_ERR(file);
    }

    old_fs = get_fs();
    set_fs(KERNEL_DS);

    if (vfs_read(file, buf, sizeof(buf), &pos) != sizeof(buf)) {
        printk(KERN_ERR "Failed to read file %s\n", filename);
    } else {
        printk(KERN_INFO "Read from %s: %s\n", filename, buf);
    }

    set_fs(old_fs);
    filp_close(file, NULL);

    return 0;
}

static void __exit my_module_exit(void) {
    printk(KERN_INFO "My module unloaded\n");
}

module_init(my_module_init);
module_exit(my_module_exit);

MODULE_LICENSE("GPL");
MODULE_DESCRIPTION("A simple Linux kernel module to read a file");