On Fri, 22 Dec 2017 13:39:11 +0100, Chris Wilson
<chris@xxxxxxxxxxxxxxxxxx> wrote:
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.
hmm, true, but then our fixed representation will include fractional
part...
but I guess it is still ok
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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