Read and write files in the Linux kernel 2

1, Kernel code

#include <linux/kernel.h>#include<linux/init.h>#include<linux/types.h>#include<linux/spinlock.h>#include<linux/blkdev.h>#include<linux/module.h>#include<linux/fs.h>#include<linux/errno.h>#include<linux/mm.h>#include<linux/cdev.h>#include<linux/sched.h>#defineIo_cmd_len 1024#defineChar_dev_name "Klog"typedefstruct {    intfile_id;//Todo    intRw_pos;//Todo    intCmd_type; intBuff_len; CharIo_buff[io_cmd_len- -];} Klog_cmd_info;#if1structFile *KLOG_FP =null;loff_t Klog_pos=0;Static intUser_cmd_proc (Char*user_cmd,Char*out_str) {Klog_cmd_info*klog_cmd = (Klog_cmd_info *) User_cmd; Klog_cmd_info*klog_ack = (Klog_cmd_info *) Out_str; if(Klog_cmd->cmd_type = =1) {//Open File        if(KLOG_FP! =null) filp_close (KLOG_FP, NULL); KLOG_FP= Filp_open (Klog_cmd->io_buff, O_RDWR | O_creat | O_trunc,0644); if(Is_err (KLOG_FP)) {PRINTK ("Filp_open error \ n"); return-1; } Klog_pos=0; sprintf (Klog_ack->io_buff,"Filp_open ok\n"); }        if(Klog_cmd->cmd_type = =2) {//Write Filemm_segment_t Old_fs; Old_fs=Get_fs (); Set_fs (Kernel_ds); //To check whyKlog_pos + = Vfs_write (KLOG_FP, Klog_cmd->io_buff, Klog_cmd->buff_len, &Klog_pos);        Set_fs (OLD_FS); sprintf (Klog_ack->io_buff,"Vfs_write ok\n"); }    if(Klog_cmd->cmd_type = =3) {//Close Filefilp_close (KLOG_FP, NULL); KLOG_FP=NULL; sprintf (Klog_ack->io_buff,"filp_close ok\n"); }        return 0;}#endif#if1intMem_open (structInode *inode,structFile *Filp) {      return 0; }    intMem_release (structInode *inode,structFile *Filp) {      return 0; }  CharUser_cmd[io_cmd_len] = {0};CharOut_str[io_cmd_len] = {0};intMem_ioctl (structFile *file, unsignedintCMD, unsignedLongArg) {PRINTK ("Mem_ioctl:%d \ n", CMD); if(Copy_from_user (User_cmd, (int*) arg, Io_cmd_len))return-Efault;        User_cmd_proc (User_cmd, OUT_STR); if(Copy_to_user (int*) arg, OUT_STR, Io_cmd_len))return-Efault; return 0;}Static intMem_major =0;struct class*pclass =NULL; structCdev My_dev; Static Const structFile_operations Mem_fops ={. Owner=this_module,. Unlocked_ioctl=mem_ioctl,. Open=Mem_open,. Release=Mem_release,}; Static intMemdev_init (void)  {      intresult; dev_t Devno= MKDEV (Mem_major,0); if(Mem_major) {/*static application Device number*/result= Register_chrdev_region (Devno,2, Char_dev_name); } Else{/*dynamically assign device numbers*/result= Alloc_chrdev_region (&devno,0,2, Char_dev_name); Mem_major=MAJOR (DEVNO); }       if(Result <0) {PRINTK ("Alloc_chrdev failed!\n"); returnresult; } cdev_init (&my_dev, &mem_fops); My_dev.owner=This_module; My_dev.ops= &Mem_fops; Cdev_add (&my_dev, MKDEV (Mem_major,0),2);/*Number of Devices 2*/Pclass=class_create (This_module, char_dev_name); if(Is_err (Pclass)) {PRINTK ("class_create failed!\n"); Gotofailed;      } device_create (Pclass, NULL, DEVNO, NULL, char_dev_name); return 0; Failed:cdev_del (&My_dev); Unregister_chrdev_region (Devno,1); returnresult; }    Static voidMemdev_exit (void) {Device_destroy (Pclass, MKDEV (Mem_major,0));        Class_destroy (Pclass); Cdev_del (&My_dev); Unregister_chrdev_region (MKDEV (Mem_major,0),2); }  #endifModule_author ("Derek Yi"); Module_license ("GPL");  Module_init (Memdev_init);  Module_exit (Memdev_exit); 

2, test the code

#include <stdio.h>#include<fcntl.h>#include<stdlib.h>#include<string.h>#include<sys/types.h>#include<sys/stat.h>#include<unistd.h>#include<sys/ioctl.h>#include<fcntl.h>#include<errno.h>#include<signal.h>#include<sys/syscall.h>#defineIo_cmd_len 1024typedefstruct {    intfile_id;//Todo    intRw_pos;//Todo    intCmd_type; intBuff_len; CharIo_buff[io_cmd_len- -];} Klog_cmd_info; Klog_cmd_info Cmd_info;intMain () {intFD; intRET =0; FD= Open ("/dev/klog", O_RDWR); if(FD <0) {printf ("Open Memdev wrong! \ n"); return 0; } sprintf (Cmd_info.io_buff,"/home/derek/klog.txt"); Cmd_info.cmd_type=1; RET= IOCTL (FD,0, &cmd_info); printf ("open:ret=%d rdata:%s\n", ret, cmd_info.io_buff);  for(inti =0; I <Ten; i++) {sprintf (Cmd_info.io_buff,"%d: ==============================\n", i); Cmd_info.buff_len=strlen (Cmd_info.io_buff); Cmd_info.cmd_type=2; RET= IOCTL (FD,0, &cmd_info); printf ("read:ret=%d rdata:%s\n", ret, cmd_info.io_buff); } Cmd_info.cmd_type=3; RET= IOCTL (FD,0, &cmd_info); printf ("close:ret=%d rdata:%s\n", ret, cmd_info.io_buff);    Close (FD); return 0;}

Read and write files in the Linux kernel 2