From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S262766AbVA1VlG (ORCPT ); Fri, 28 Jan 2005 16:41:06 -0500 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S262768AbVA1VlG (ORCPT ); Fri, 28 Jan 2005 16:41:06 -0500 Received: from web41411.mail.yahoo.com ([66.218.93.77]:53132 "HELO web41411.mail.yahoo.com") by vger.kernel.org with SMTP id S262766AbVA1Vkx (ORCPT ); Fri, 28 Jan 2005 16:40:53 -0500 Comment: DomainKeys? See http://antispam.yahoo.com/domainkeys DomainKey-Signature: a=rsa-sha1; q=dns; c=nofws; s=s1024; d=yahoo.com; b=tsYb4zpB2P/6AwE7awhE+7Myq5wXUw6bRL1K/wNq0pGpWwphV3vkr13H/REQ7mSjO6ixcXh/nnHafqoguRWZ9qMUipUMdig7u67brOP/GyhlJ9D6bl1pyGcZ5lbe+QD831qcbQSgB8wT2jbHBgpWwDGMSIHP8rD6N0dokJb4vXw= ; Message-ID: <20050128214051.34768.qmail@web41411.mail.yahoo.com> Date: Fri, 28 Jan 2005 13:40:51 -0800 (PST) From: Rock Gordon Subject: Re: userspace vs. kernelspace address To: Jan Hudec Cc: linux-kernel@vger.kernel.org, kernelnewbies@nl.linux.org, Bernd Petrovitsch In-Reply-To: <20050128075209.GA14153@vagabond> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Sender: linux-kernel-owner@vger.kernel.org X-Mailing-List: linux-kernel@vger.kernel.org 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 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 > > 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