Re: [Linaro-mm-sig] [PATCHv2 4/4] staging: android: ion: Add ioctl to query available heaps
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
Re: [Linaro-mm-sig] [PATCHv2 4/4] staging: android: ion: Add ioctl to query available heaps
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
Re: [Linaro-mm-sig] [PATCHv2 4/4] staging: android: ion: Add ioctl to query available heaps
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
Re: [Linaro-mm-sig] [PATCHv2 4/4] staging: android: ion: Add ioctl to query available heaps
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
