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powerpc/uaccess: Allow get_user() with bitwise types

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At the moment, if p and x are both of the same bitwise type
(eg. __le32), get_user(x, p) produces a sparse warning.

This is because *p is loaded into a long then cast back to typeof(*p).

When typeof(*p) is a bitwise type (which is uncommon), such a cast needs
__force, otherwise sparse produces a warning.

For non-bitwise types __force should have no effect, and should not hide
any legitimate errors.

Note that we are casting to typeof(*p) not typeof(x). Even with the
cast, if x and *p are of different types we should get the warning, so I
think we are not loosing the ability to detect any actual errors.

virtio would like to use bitwise types with get_user() so fix these
spurious warnings by adding __force.

Signed-off-by: Michael S. Tsirkin <mst@redhat.com>
[mpe: Fill in changelog with more details]
Signed-off-by: Michael Ellerman <mpe@ellerman.id.au>
This commit is contained in:
Michael S. Tsirkin 2014-12-14 18:52:51 +02:00 committed by Michael Ellerman
parent c8742f8512
commit 505e428374
1 changed files with 3 additions and 3 deletions
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6
arch/powerpc/include/asm/uaccess.h
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@ -284,7 +284,7 @@ do { \
if (!is_kernel_addr((unsigned long)__gu_addr)) \
might_fault(); \
__get_user_size(__gu_val, __gu_addr, (size), __gu_err); \
(x) = (__typeof__(*(ptr)))__gu_val; \
(x) = (__force __typeof__(*(ptr)))__gu_val; \
__gu_err; \
})
#endif /* __powerpc64__ */
@ -297,7 +297,7 @@ do { \
might_fault(); \
if (access_ok(VERIFY_READ, __gu_addr, (size))) \
__get_user_size(__gu_val, __gu_addr, (size), __gu_err); \
(x) = (__typeof__(*(ptr)))__gu_val; \
(x) = (__force __typeof__(*(ptr)))__gu_val; \
__gu_err; \
})
@ -308,7 +308,7 @@ do { \
const __typeof__(*(ptr)) __user *__gu_addr = (ptr); \
__chk_user_ptr(ptr); \
__get_user_size(__gu_val, __gu_addr, (size), __gu_err); \
(x) = (__typeof__(*(ptr)))__gu_val; \
(x) = (__force __typeof__(*(ptr)))__gu_val; \
__gu_err; \
})