On Thu, Oct 02, 2003 at 10:27:28AM +0200, Jan Hudec wrote: > On Tue, Sep 30, 2003 at 13:02:42 +0530, Pradheep K E wrote: > > hi, > > i'm getting a strange problem while writing to a file from a LKM. > > could anyone tell me how exactly do we write to a file in the kernel mode. > > this code just created the file but didn't write anything to it. > > > > struct file* f= filp_open(filename, O_CREAT|O_APPEND, 0600); > > f->f_op->write(f, "foo", 3, &f->fpos); > > filp_close(f, NULL); > > > > the write function returned -14, and i dont know why it's giving me a > > problem. is there anything more that i should do before writing to the > > file? > > You really SHOULDN'T be doing this. However, it _is_doable_. I'd like to repeat that. If you are writing to a file fromt the kernel, you need to need to reevaluate the design. > First, look up the value 14 in errno.h -- EFAULT. > Hm... that suggests the buffer is not accessible. And it is NOT, because > it's in wrong segment. Look up the kernel_DS or some such thing. That > will allow copy_from_user copy from kernel address space. The grossly misnamed get_fs() and set_fs() will come in handy here. Grep around to see how they are used. -- Muli Ben-Yehuda http://www.mulix.org
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