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: sta...@vger.kernel.org
Signed-off-by: Rasmus Villemoes <li...@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 */
--
2.15.1
