On 03/09/18 13:34, Andrey Konovalov wrote: > On Fri, Aug 31, 2018 at 3:42 PM, Al Viro <viro@xxxxxxxxxxxxxxxxxx> wrote: >> On Fri, Aug 31, 2018 at 10:11:24AM +0200, Luc Van Oostenryck wrote: >>> On Thu, Aug 30, 2018 at 01:41:16PM +0200, Andrey Konovalov wrote: >>>> This patch adds __force annotations for __user pointers casts detected by >>>> sparse with the -Wcast-from-as flag enabled (added in [1]). >>>> >>>> [1] https://github.com/lucvoo/sparse-dev/commit/5f960cb10f56ec2017c128ef9d16060e0145f292 >>> >>> Hi, >>> >>> It would be nice to have some explanation for why these added __force >>> are useful. > > I'll add this in the next version, thanks! > >> It would be even more useful if that series would either deal with >> the noise for real ("that's what we intend here, that's what we intend there, >> here's a primitive for such-and-such kind of cases, here we actually >> ought to pass __user pointer instead of unsigned long", etc.) or left it >> unmasked. >> >> As it is, __force says only one thing: "I know the code is doing >> the right thing here". That belongs in primitives, and I do *not* mean the >> #define cast_to_ulong(x) ((__force unsigned long)(x)) >> kind. >> >> Folks, if you don't want to deal with that - leave the warnings be. >> They do carry more information than "someone has slapped __force in that place". >> >> Al, very annoyed by that kind of information-hiding crap... > > This patch only adds __force to hide the reports I've looked at and > decided that the code does the right thing. The cases where this is > not the case are handled by the previous patches in the patchset. I'll > this to the patch description as well. Is that OK? > I think as well that we should make explicit the information that __force is hiding. A possible solution could be defining some new address spaces and use them where it is relevant in the kernel. Something like: # define __compat_ptr __attribute__((noderef, address_space(5))) # define __tagged_ptr __attribute__((noderef, address_space(6))) In this way sparse can still identify the casting and trigger a warning. We could at that point modify sparse to ignore these conversions when a specific flag is passed (i.e. -Wignore-compat-ptr, -Wignore-tagged-ptr) to exclude from the generated warnings the ones we have already dealt with. What do you think about this approach? > _______________________________________________ > linux-arm-kernel mailing list > linux-arm-kernel@xxxxxxxxxxxxxxxxxxx > http://lists.infradead.org/mailman/listinfo/linux-arm-kernel > -- Regards, Vincenzo
