linux内核空间 打开、读、写等文件操作实现

#include <linux/config.h>

#include <linux/module.h>

#include <linux/fs.h>

#include <linux/sched.h>

#include <linux/file.h>

#include <asm/processor.h>

#include <asm/uaccess.h>

 

/*

  file I/O in kernel module

*/

#define EOF (-1)

#define SEEK_SET 0

#define SEEK_CUR 1

#define SEEK_END 2

 

// Context : User

// Parameter :

// filename : filename to open

// flags :

// O_RDONLY, O_WRONLY, O_RDWR

// O_CREAT, O_EXCL, O_TRUNC, O_APPEND, O_NONBLOCK, O_SYNC, ...

// mode : file creation permission.

// S_IRxxx S_IWxxx S_IXxxx (xxx = USR, GRP, OTH), S_IRWXx (x = U, G, O)

// Return :

// file pointer. if error, return NULL

 

struct file *klib_fopen(const char *filename, int flags, int mode)

{ 

    struct file *filp = filp_open(filename, flags, mode);

 

    return (IS_ERR(filp)) ? NULL : filp;

}

 

// Context : User

// Parameter :

// filp : file pointer

// Return :

void klib_fclose(struct file *filp)

{

    if (filp)

        fput(filp);

}

 

// Context : User

// Parameter :

// filp : file pointer

// offset :

// whence : SEEK_SET, SEEK_CUR

// Comment :

// do not support SEEK_END

// no boundary check (file position may exceed file size)

int klib_fseek(struct file *filp, int offset, int whence)

{

 

    int pos = filp->f_pos;

 

    if (filp) {

 

        if (whence == SEEK_SET)

            pos = offset;

        else if (whence == SEEK_CUR)

            pos = offset;

 

        if (pos < 0)

            pos = 0;

 

        return (filp->f_pos = pos);

    } else

        return -ENOENT;

 

}

 

// Context : User

// Parameter :

// buf : buffer to read into

// len : number of bytes to read

// filp : file pointer

// Return :

// actually read number. 0 = EOF, negative = error

int klib_fread(char *buf, int len, struct file *filp)

{

    int readlen;

 

    mm_segment_t oldfs;

 

    if (filp == NULL)

        return -ENOENT;

 

    if (filp->f_op->read == NULL)

        return -ENOSYS;

 

    if (((filp->f_flags & O_ACCMODE) & O_RDONLY) != 0)

        return -EACCES;

 

    oldfs = get_fs();

    set_fs(KERNEL_DS);

 

    readlen = filp->f_op->read(filp, buf, len, &filp->f_pos);

 

    set_fs(oldfs);

 

    return readlen;

}

 

// Context : User

// Parameter :

// filp : file pointer

// Return :

// read character, EOF if end of file

 

int klib_fgetc(struct file *filp)

{

 

    int len;

    unsigned char buf[4];

 

    len = klib_fread((char *)buf, 1, filp);

 

    if (len > 0)

        return buf[0];

    else if (len == 0)

        return EOF;

    else

        return len;

}

 

// Context : User

// Parameter :

// str : string

// size : size of str buffer

// filp : file pointer

// Return :

// read string. NULL if end of file

// Comment :

// Always append trailing null character

 

char *klib_fgets(char *str, int size, struct file *filp)

{

 

    char *cp;

    int len, readlen;

    mm_segment_t oldfs;

 

    if (filp && filp->f_op->read

        && ((filp->f_flags & O_ACCMODE) & O_WRONLY) == 0) {

        oldfs = get_fs();

        set_fs(KERNEL_DS);

 

        for (cp = str, len = -1, readlen = 0; readlen < size - 1;

             cp, readlen) {

 

            if ((len =

                 filp->f_op->read(filp, cp, 1, &filp->f_pos)) <= 0)

                break;

 

            if (*cp == '/n') {

                cp;

                readlen;

                break;

 

            }

        }

 

        *cp = 0;

        set_fs(oldfs);

 

        return (len < 0 || readlen == 0) ? NULL : str;

    } else

        return NULL;

 

}

 

// Context : User

// Parameter :

// buf : buffer containing data to write

// len : number of bytes to write

// filp : file pointer

// Return :

// actually written number. 0 = retry, negative = error

 

int klib_fwrite(char *buf, int len, struct file *filp)

{

    int writelen;

    mm_segment_t oldfs;

 

    if (filp == NULL)

        return -ENOENT;

 

    if (filp->f_op->write == NULL)

        return -ENOSYS;

 

    if (((filp->f_flags & O_ACCMODE) & (O_WRONLY | O_RDWR)) == 0)

        return -EACCES;

 

    oldfs = get_fs();

    set_fs(KERNEL_DS);

    writelen = filp->f_op->write(filp, buf, len, &filp->f_pos);

    set_fs(oldfs);

 

    return writelen;

}

 

// Context : User

// Parameter :

// filp : file pointer

// Return :

// written character, EOF if error

int klib_fputc(int ch, struct file *filp)

{

    int len;

    unsigned char buf[4];

 

    buf[0] = (unsigned char)ch;

    len = klib_fwrite(buf, 1, filp);

 

    if (len > 0)

        return buf[0];

    else

        return EOF;

}

 

// Context : User

// Parameter :

// str : string

// filp : file pointer

// Return :

// count of written characters. 0 = retry, negative = error

int klib_fputs(char *str, struct file *filp)

{

    return klib_fwrite(str, strlen(str), filp);

}

 

// Context : User

// Parameter :

// filp : file pointer

// fmt : printf() style formatting string

// Return :

// same as klib_fputs()

int klib_fprintf(struct file *filp, const char *fmt, ...)

{

    static char s_buf[1024];

 

    va_list args;

    va_start(args, fmt);

    vsprintf(s_buf, fmt, args);

    va_end(args);

    return klib_fputs(s_buf, filp);

}