On Fri, Apr 07, 2017 at 09:14:29AM -0700, Andy Lutomirski wrote: > I think we're approaching this all wrong, actually. The fact that x86 > has this CR0.WP thing is arguably a historical accident, and the fact > that PaX uses it doesn't mean that PaX is doing it the best way for > upstream Linux. > > Why don't we start at the other end and do a generic non-arch-specific > implementation: set up an mm_struct that contains an RW alias of the > relevant parts of rodata and use use_mm to access it. (That is, > get_fs() to back up the old fs, set_fs(USER_DS), > use_mm(&rare_write_mm), do the write using copy_to_user, undo > everything.)
FWIW, I completely agree with this approach. That's largely the approach arm64 would have to take regardless (as per Hoeun's patches), and having a consistent common implementation would be desireable. There are a couple of other complications to handle (e.g. a perf interrupt coming in and trying to read from the mapping), but I think we can handle that generically. Thanks, Mark.
