On Sat, Jun 17, 2023 at 09:38:17AM -0700, Song Liu wrote: > On Sat, Jun 17, 2023 at 8:37 AM Kent Overstreet > <kent.overstreet@xxxxxxxxx> wrote: > > > > On Sat, Jun 17, 2023 at 09:57:59AM +0300, Mike Rapoport wrote: > > > > This is growing fast. :) We have 3 now: text, data, jit. And it will be > > > > 5 when we split data into rw data, ro data, ro after init data. I wonder > > > > whether we should still do some type enum here. But we can revisit > > > > this topic later. > > > > > > I don't think we'd need 5. Four at most :) > > > > > > I don't know yet what would be the best way to differentiate RW and RO > > > data, but ro_after_init surely won't need a new type. It either will be > > > allocated as RW and then the caller will have to set it RO after > > > initialization is done, or it will be allocated as RO and the caller will > > > have to do something like text_poke to update it. > > > > Perhaps ro_after_init could use the same allocation interface and share > > pages with ro pages - if we just added a refcount for "this page > > currently needs to be rw, module is still loading?" > > If we don't relax rules with read only, we will have to separate rw, ro, > and ro_after_init. But we can still have page sharing: > > Two modules can put rw data on the same page. > With text poke (ro data poke to be accurate), two modules can put > ro data on the same page. > > > text_poke() approach wouldn't be workable, you'd have to audit and fix > > all module init code in the entire kernel. > > Agreed. For this reason, each module has to have its own page(s) for > ro_after_init data. Relaxing page permissions to allow for page sharing could also be a config option. For archs with 64k pages it seems worthwhile.
