Messages in this thread | | | Subject | Re: [Linaro-mm-sig] [PATCHv2 4/4] staging: android: ion: Add ioctl to query available heaps | From | Laura Abbott <> | Date | Fri, 2 Sep 2016 14:53:52 -0700 |
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On 09/02/2016 02:37 PM, Arnd Bergmann wrote: > On Friday, September 2, 2016 2:27:21 PM CEST Laura Abbott wrote: >>> >>> All warnings (new ones prefixed by >>): >>> >>> drivers/staging/android/ion/ion.c: In function 'ion_query_heaps': >>>>> drivers/staging/android/ion/ion.c:1181:3: warning: cast to pointer from integer of different size [-Wint-to-pointer-cast] >>> (struct ion_heap_data __user *)query->heaps; >>> ^ >>> >> >> botching-up-ioctls.txt says: >> >> * Pointers are __u64, cast from/to a uintprt_t on the userspace side and >> from/to a void __user * in the kernel. Try really hard not to delay this >> conversion or worse, fiddle the raw __u64 through your code since that >> diminishes the checking tools like sparse can provide. >> >> This doesn't seem like it will work on 32-bit systems since you'll end up >> with the warning above. Is there a better option or did I misunderstand >> how that is supposed to work? >> > > I don't know a better way that two cast, doing > > (struct ion_heap_data __user *)(uintptr_t)query->heaps; > > It may help to put this into an inline function though. > > Arnd >
There already is one it turns out in kernel.h:
#define u64_to_user_ptr(x) ( \ { \ typecheck(u64, x); \ (void __user *)(uintptr_t)x; \ } \ )
At least this way I don't have to look at the double casts.
Thanks, Laura
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