From mboxrd@z Thu Jan 1 00:00:00 1970 Date: Tue, 31 Jul 2007 06:35:29 +0100 (BST) From: Mark Fortescue Subject: Re: [SPARC32] NULL pointer derefference In-Reply-To: <20070729.211929.78713482.davem@davemloft.net> Message-ID: References: <20070729.211929.78713482.davem@davemloft.net> MIME-Version: 1.0 Content-Type: TEXT/PLAIN; charset=US-ASCII; format=flowed Sender: owner-linux-mm@kvack.org Return-Path: To: David Miller Cc: aaw@google.com, akpm@linux-foundation.org, linux-arch@vger.kernel.org, sparclinux@vger.kernel.org, wli@holomorphy.com, linux-mm@kvack.org, linux-kernel@vger.kernel.org List-ID: Hi David, > > One possible issue is sequencing, perhaps the stack argument copy > is occuring before the new context is setup properly on sun4c. > I think it is somthing related to this but too much has changed for me to work out what is going on. At present, I don't have a good enough understanding of the virtual memory system and how it interracts with the sun4c mmu. The original code did a job lot of pte stuf in install_arg_page. The new code seems to replace this using get_user_pages but I have not worked out how get_user_pages gets to the point at which it allocated pte's i.e. maps the stack memory it is about to put the arguments into. > Another issue might be the new flush_cache_page() call in this > new code in fs/exec.c, there are now cases where flush_cache_page() > will be called on kernel addresses, and sun4c's implementation might > not like that at all. I commented out the flush_cache_page callmade in the new code. This had no effect on the problem. Other tests have shown it is breaking earlier than this. I am going to try to narrow down exactly where the pointer gets messed up as this should help. Regards Mark Fortescue. -- To unsubscribe, send a message with 'unsubscribe linux-mm' in the body to majordomo@kvack.org. For more info on Linux MM, see: http://www.linux-mm.org/ . Don't email: email@kvack.org