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random32: Fix implicit truncation warning in prandom_seed_state()

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sparse generates the following warning:

 include/linux/prandom.h:114:45: sparse: sparse: cast truncates bits from
 constant value

This is because the 64-bit seed value is manipulated and then placed in a
u32, causing an implicit cast and truncation. A forced cast to u32 doesn't
prevent this warning, which is reasonable because a typecast doesn't prove
that truncation was expected.

Logical-AND the value with 0xffffffff to make explicit that truncation to
32-bit is intended.

Reported-by: kernel test robot <lkp@intel.com>
Signed-off-by: Richard Fitzgerald <rf@opensource.cirrus.com>
Reviewed-by: Petr Mladek <pmladek@suse.com>
Signed-off-by: Petr Mladek <pmladek@suse.com>
Link: https://lore.kernel.org/r/20210525122012.6336-3-rf@opensource.cirrus.com
This commit is contained in:
Richard Fitzgerald 2021-05-25 13:20:12 +01:00 committed by Petr Mladek
parent 1b932689c7
commit d327ea15a3
1 changed files with 1 additions and 1 deletions
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2
include/linux/prandom.h
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@ -111,7 +111,7 @@ static inline u32 __seed(u32 x, u32 m)
*/
static inline void prandom_seed_state(struct rnd_state *state, u64 seed)
{
u32 i = (seed >> 32) ^ (seed << 10) ^ seed;
u32 i = ((seed >> 32) ^ (seed << 10) ^ seed) & 0xffffffffUL;
state->s1 = __seed(i, 2U);
state->s2 = __seed(i, 8U);