The last expression in a statement expression need not be a bare variable, quoting gcc docs
The last thing in the compound statement should be an expression followed by a semicolon; the value of this subexpression serves as the value of the entire construct.
and we already use that in e.g. the min/max macros which end with a ternary expression.
This way, we can allow index to have const-qualified type, which will in some cases avoid the need for introducing a local copy of index of non-const qualified type. That, in turn, can prevent readers not familiar with the internals of array_index_nospec from wondering about the seemingly redundant extra variable, and I think that's worthwhile considering how confusing the whole _nospec business is.
The expression _i&_mask has type unsigned long (since that is the type of _mask, and the BUILD_BUG_ONs guarantee that _i will get promoted to that), so in order not to change the type of the whole expression, add a cast back to typeof(_i).
Cc: stable@vger.kernel.org Signed-off-by: Rasmus Villemoes linux@rasmusvillemoes.dk --- cc stable because if this is ok, there will probably be future users relying on this which also get cc'ed to -stable.
include/linux/nospec.h | 3 +-- 1 file changed, 1 insertion(+), 2 deletions(-)
diff --git a/include/linux/nospec.h b/include/linux/nospec.h index fbc98e2c8228..132e3f5a2e0d 100644 --- a/include/linux/nospec.h +++ b/include/linux/nospec.h @@ -72,7 +72,6 @@ static inline unsigned long array_index_mask_nospec(unsigned long index, BUILD_BUG_ON(sizeof(_i) > sizeof(long)); \ BUILD_BUG_ON(sizeof(_s) > sizeof(long)); \ \ - _i &= _mask; \ - _i; \ + (typeof(_i)) (_i & _mask); \ }) #endif /* _LINUX_NOSPEC_H */