From mboxrd@z Thu Jan 1 00:00:00 1970 From: labbott@redhat.com (Laura Abbott) Date: Fri, 6 Nov 2015 15:41:57 -0800 Subject: [PATCH] arm: Use kernel mm when updating section permissions In-Reply-To: <20151106204641.GT8644@n2100.arm.linux.org.uk> References: <1446685239-28522-1-git-send-email-labbott@fedoraproject.org> <20151105094615.GP8644@n2100.arm.linux.org.uk> <563B81DA.2080409@redhat.com> <20151105162719.GQ8644@n2100.arm.linux.org.uk> <563BFCC4.8050705@redhat.com> <563CF510.9080506@redhat.com> <20151106204641.GT8644@n2100.arm.linux.org.uk> Message-ID: <563D3AC5.4020203@redhat.com> To: linux-arm-kernel@lists.infradead.org List-Id: linux-arm-kernel.lists.infradead.org On 11/06/2015 12:46 PM, Russell King - ARM Linux wrote: > On Fri, Nov 06, 2015 at 10:44:32AM -0800, Laura Abbott wrote: >> with my test patch. I think setting both current->active_mm and &init_mm >> is sufficient. Maybe explicitly setting swapper_pg_dir would be cleaner? > > Please, stop thinking like this. If you're trying to change the kernel > section mappings after threads have been spawned, you need to change > them for _all_ threads, which means you need to change them for every > page table that's in existence at that time - you can't do just one > table and hope everyone updates, it doesn't work like that. > That's a bad assumption assumption on my part based on what I was observing. At the time of mark_rodata_ro, the only threads present are kernel threads which aren't going to have task->mm. Only the running thread is going to have active_mm. None of those are init_mm. To be complete we need: - Update every task->mm for every thread in every process - Update current->active_mm - Update &init_mm explicitly All this would need to be done under stop_machine as well. Does that cover everything or am I still off? Thanks, Laura