Are you trying to access the userspace from kernel thread (created by kernel_thread) ? I do not think it is possible. Kernel threads do not have user address space. Arun -----Original Message----- From: kernelnewbies-bounce@xxxxxxxxxxxx [mailto:kernelnewbies-bounce@xxxxxxxxxxxx]On Behalf Of Rock Gordon Sent: Saturday, January 29, 2005 3:11 AM To: Jan Hudec Cc: linux-kernel@xxxxxxxxxxxxxxx; kernelnewbies@xxxxxxxxxxxx; Bernd Petrovitsch Subject: Re: userspace vs. kernelspace address Hi everbody, Thanks for your replies. Lemme explain my problem a little bit more .... I have a thread that does exactly similar things in kernel-mode and user-mode (depending on how you invoked it; of course, the kernel one is forked using kernel_thread(), and the user one is from pthread_create()). The architecture-dependant stuff is taken care of by extensive use of __KERNEL__ macro testing. This particular thread gets a packet of data, the header of which contains address to where it should be copying the payload associated with that packet. The kernel-mode thread will need to decide how to copy data into another process' address space, so will the user-mode thread. However I think my copy_to_user and copy_from_user are failing since the kernel-mode thread is copying data into another process's address space, and I am not sure how to do this. Do the get_fs() and set_fs() combinations let you do that? If not, then how do I do it? Something like when you invoke the ->write or ->read functions, you need to copy the requisite data into the buffer the application provided you with. Thanks and regards, Rock --- Jan Hudec <bulb@xxxxxx> wrote: > On Fri, Jan 28, 2005 at 01:06:21 +0100, Bernd > Petrovitsch wrote: > > On Thu, 2005-01-27 at 09:14 -0800, Rock Gordon > wrote: > > > If I'm given a particular address, how do I test > > > whether that address is from userspace or from > kernel > > > space? > > > > You don't. > > > > > I need to make these decisions from either > inside a > > > kernel module or a userspace program. The idea > is I > > > use memcpy() in the user-user version, > > > copy_from/to_user in the kernel-kernel version, > and > > > prohibit the others. > > > > You need to know where the address is from and use > the correct function. > > If the interface is defined as taking userland > address, than kernel > function passing a kernel address in is responsible > for calling > set_fs(KERNEL_DS) before and undoing it after. That > way the > copy_to/from_user does not complain. > > ---------------------------------------------------------------------------- --- > Jan 'Bulb' Hudec <bulb@xxxxxx> > > ATTACHMENT part 2 application/pgp-signature name=signature.asc __________________________________ Do you Yahoo!? Take Yahoo! Mail with you! Get it on your mobile phone. http://mobile.yahoo.com/maildemo -- Kernelnewbies: Help each other learn about the Linux kernel. Archive: http://mail.nl.linux.org/kernelnewbies/ FAQ: http://kernelnewbies.org/faq/ -- Kernelnewbies: Help each other learn about the Linux kernel. Archive: http://mail.nl.linux.org/kernelnewbies/ FAQ: http://kernelnewbies.org/faq/
