-----BEGIN PGP SIGNED MESSAGE----- Hash: SHA1 On Fri, 2007-09-21 at 11:32 -0500, Sachin Gaikwad wrote: ssize_t (*read) (struct file *, char __user *, size_t, loff_t *); > ... So what does extra __user specify here. > It's a reminder that you have to use copy_to_user when you want to write to this buffer. The memory area may be non-existant or swapped out. copy_to_user deals with that. (There is also a possible race when one user-space Thread calls read and another calls free - copy_to_user also deals with that?) If I have to use this function of reading file inside the kernel, then > shall I pass kernel buffer to it or user space buffer ? > > I know that it is VERY BAD idea to read from kernel. > Yes, it is. Why do you want that? But how are we suppposed to do it if at all. > I've heard from http://lwn.net/Articles/248430/ that you can do it sys_open() and sys_read(). Michael Blizek -----BEGIN PGP SIGNATURE----- Version: GnuPG v1.4.6 (GNU/Linux) iD8DBQFG9Bg/1o5nKJ0vLIQRAi5iAJ4z0idpJMAM5ymiJQP9zjuU4qezDgCghzHZ AOfHgn976UI0qbVwn4nP9IU= =Uifx -----END PGP SIGNATURE----- -- To unsubscribe from this list: send an email with "unsubscribe kernelnewbies" to ecartis@xxxxxxxxxxxx Please read the FAQ at http://kernelnewbies.org/FAQ
