The problem over is not of kernel thread but of sys_open. The string that
u pass to sys_open should be from userspace and not from the kernel space.
When you use sys_open, there is check in the kernel to see whenther the
address of the string is a userspace address or not.
HTH,
Raghu
On Sat, 12 Jul 2003, kernel rakshakudu wrote:
> Hi,
> I am writing a kernel thread which opens a file and
> writes into it everytime in a continous loop. The
> Kernel thread is started by a system call.
>
> The problem is the file openning by Kernel thread
> fails and sys_open() returns -14 (EFAULT). Can any
> body help me in this ??? Also if you know any url
> where there is good discussion or documentation of
> kernel threads, keventd , let me know.
>
> source is as follows:
>
> static void example_thread()
> {
>
>
> int i,error,fd,num;
> char c;
> daemonize();
> strcpy(current->comm,"examplethread");
> printk("This is test log message by
> example_thread\n");
>
> for(;;)
> {
>
> fd=sys_open("/tmp/examplethread",O_CREAT |
> O_WRONLY,S_IRWXU);
> printk("Fd of the file:%d\n",fd);
> if (fd>=0)
> {
>
> num=sys_write(fd,"This is test log",100);
>
> }
> else
> {
> printk("/tmp/examplethread failed to open\n");
> goto out;
>
> }
>
> sys_close(fd);
> current->state = TASK_INTERRUPTIBLE;
> schedule();
> }
> printk("The second message is read from log
> buffer\n");
>
> out:
> printk("example_thread exiting\n");
> }
>
>
> asmlinkage int sys_startkthread( )
> {
> pid_t pid;
> pid = kernel_thread(example_thread,NULL,CLONE_FS |
> CLONE_FILES | CLONE_SIGNAL);
> if (pid < 0)
> return -1;
> return pid;
>
> }
>
>
> thanks in advance,
> KR
>
> =====
>
> "Conquering Myselves to Conquer The World"
>
> "Securing Kernel to Secure Whole System"
>
>
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