On 03/09/18 13:34, Andrey Konovalov wrote:
On Fri, Aug 31, 2018 at 3:42 PM, Al Viro viro@zeniv.linux.org.uk 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/5f960cb10f56ec2017c128ef9d16060e...
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 withthe 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 doingthe 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?
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