Quoting Michal Wajdeczko (2017-12-22 12:25:55)
> If someone provides too large number for fixed16 type
> we will WARN but we will not correctly clamp values
> and that may lead to fully wrong calculations.
>
> Signed-off-by: Michal Wajdeczko <michal.wajdeczko@xxxxxxxxx>
> Cc: Chris Wilson <chris@xxxxxxxxxxxxxxxxxx>
> Cc: Rodrigo Vivi <rodrigo.vivi@xxxxxxxxx>
> Cc: Joonas Lahtinen <joonas.lahtinen@xxxxxxxxxxxxxxx>
> ---
> drivers/gpu/drm/i915/fixed16_16.h | 13 +++++++++----
> 1 file changed, 9 insertions(+), 4 deletions(-)
>
> diff --git a/drivers/gpu/drm/i915/fixed16_16.h b/drivers/gpu/drm/i915/fixed16_16.h
> index af23997..43fe0037 100644
> --- a/drivers/gpu/drm/i915/fixed16_16.h
> +++ b/drivers/gpu/drm/i915/fixed16_16.h
> @@ -57,7 +57,8 @@ static inline fixed16_16_t u32_to_fixed16(u32 val)
> {
> fixed16_16_t fp;
>
> - WARN_ON(val > U16_MAX);
> + if (WARN_ON(val > U16_MAX))
> + val = U16_MAX;
return FIXED16_16_MAX;
If val is too large, the closest we can get to val in our representation
is 16_16_MAX.
>
> fp.val = val << 16;
> return fp;
return TO_FIXED16_16(val << 16);
> @@ -93,7 +94,9 @@ static inline fixed16_16_t clamp_u64_to_fixed16(u64 val)
> {
> fixed16_16_t fp;
>
> - WARN_ON(val > U32_MAX);
> + if (WARN_ON(val > U32_MAX))
> + val = U32_MAX;
I would do the early return. Perhaps check with gcc if prefers returning
a constant than the jump back?
-Chris
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