[Mesa-dev] [PATCH] intel: Avoid divide by zero for very small linear blits

[Ian Romanick]

From: Ian Romanick 

If size is small (such as 1),

   pitch = ROUND_DOWN_TO(MIN2(size, (1 << 15) - 1), 4);

makes pitch = 0.  Then

   height = size / pitch;

causes a division-by-zero exception.  If pitch is zero, set height to
1 and avoid the division.

This fixes piglit's bin/getteximage-formats test and glean's
bufferObject test.

NOTE: This is a candidate for the 8.0 release branch.

Signed-off-by: Ian Romanick 
Bugzilla: https://bugs.freedesktop.org/show_bug.cgi?id=44971
---
 src/mesa/drivers/dri/intel/intel_blit.c |2 +-
 1 files changed, 1 insertions(+), 1 deletions(-)

diff --git a/src/mesa/drivers/dri/intel/intel_blit.c 
b/src/mesa/drivers/dri/intel/intel_blit.c
index 9eacadd..fd4a86c 100644
--- a/src/mesa/drivers/dri/intel/intel_blit.c
+++ b/src/mesa/drivers/dri/intel/intel_blit.c
@@ -492,7 +492,7 @@ intel_emit_linear_blit(struct intel_context *intel,
 * rounding that down to the nearest DWORD is 1 << 15 - 4
 */
pitch = ROUND_DOWN_TO(MIN2(size, (1 << 15) - 1), 4);
-   height = size / pitch;
+   height = (pitch == 0) ? 1 : size / pitch;
ok = intelEmitCopyBlit(intel, 1,
  pitch, src_bo, src_offset, I915_TILING_NONE,
  pitch, dst_bo, dst_offset, I915_TILING_NONE,
-- 
1.7.6.4

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Re: [Mesa-dev] [PATCH] intel: Avoid divide by zero for very small linear blits

[Eric Anholt]

On Thu,  2 Feb 2012 16:50:32 -0700, "Ian Romanick"  wrote:
> From: Ian Romanick 
> 
> If size is small (such as 1),
> 
>pitch = ROUND_DOWN_TO(MIN2(size, (1 << 15) - 1), 4);
> 
> makes pitch = 0.  Then
> 
>height = size / pitch;
> 
> causes a division-by-zero exception.  If pitch is zero, set height to
> 1 and avoid the division.
> 
> This fixes piglit's bin/getteximage-formats test and glean's
> bufferObject test.

Looks simpler than my patch, while correct.

Reviewed-by: Eric Anholt 


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