Messages in this thread | | | Subject | Re: [PATCH] arm: Use kernel mm when updating section permissions | From | Laura Abbott <> | Date | Fri, 6 Nov 2015 15:41:57 -0800 |
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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
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