linux 内核驱动加载过程中 向文件系统中的文件进行读写操作

utils.h 文件:

#ifndef __UTILS_H__
#define __UTILS_H__

void a2f(const char *s, ...);

#endif

utils.c 文件:

#include <linux/fs.h>
#include <asm/segment.h>
#include <asm/uaccess.h>
#include <linux/buffer_head.h>
#include <linux/string.h>

#include "utils.h"

#define FILE_PATH "/hzh"

static struct file *fp;

static int open_it() {
    if (fp) return 0;
    mm_segment_t oldfs;
    int err = 0;

    oldfs = get_fs();
    set_fs(get_ds());
    fp = filp_open(FILE_PATH, O_CREAT|O_RDWR|O_APPEND, 0); // 以追加方式写入文件
    set_fs(oldfs);
    if (IS_ERR(fp)) {
        err = PTR_ERR(fp);
        return 1;
    }

    return 0;
}

static void close_it() {
    if (!fp) return;
    filp_close(fp, 0);
    fp = 0;
}

static int read_it(unsigned long long offset, unsigned char *data, unsigned int size) {
    if (!fp) return 0;
    mm_segment_t oldfs;
    int ret;

    oldfs = get_fs();
    set_fs(get_ds());

    ret = vfs_read(fp, data, size, &offset);

    set_fs(oldfs);
    return ret;
}

static int write_it(unsigned long long offset, unsigned char *data, unsigned int size) {
    if (!fp) return 0;
    mm_segment_t oldfs;
    int ret;

    oldfs = get_fs();
    set_fs(get_ds());

    ret = vfs_write(fp, data, size, &offset);

    set_fs(oldfs);
    return ret;
}

static int sync_it() {
    if (!fp) return 0;
    vfs_fsync(fp, 0);
    return 0;
}

void a2f(const char *fmt, ...) {
    if (open_it()) return;

    char print_buf[1024];
    va_list args;
    int printed;
    //初始化args，使其指向可变参数的第一个参数，fmt是可变参数的前一个参数
    va_start(args, fmt); 
    printed = vsprintf(print_buf, fmt, args);
    va_end(args);

    write_it(0, print_buf, printed);
    sync_it();

    // close_it();
}