[Mesa-dev] [PATCH v2] mesa: error out in indirect draw when vertex bindings mismatch

[Fredrik Höglund]

On Thursday 19 November 2015, Tapani Pälli wrote:
> Patch adds additional mask for tracking which vertex buffer bindings
> are set. This array can be directly compared to which vertex arrays
> are enabled and should match when drawing.
> 
> Fixes following CTS tests:
> 
>    ES31-CTS.draw_indirect.negative-noVBO-arrays
>    ES31-CTS.draw_indirect.negative-noVBO-elements
> 
> v2: update mask in vertex_array_attrib_binding
> 
> Signed-off-by: Tapani Pälli <tapani.palli at intel.com>
> ---
>  src/mesa/main/api_validate.c | 13 +++++++++++++
>  src/mesa/main/mtypes.h       |  3 +++
>  src/mesa/main/varray.c       |  7 +++++++
>  3 files changed, 23 insertions(+)
> 
> diff --git a/src/mesa/main/api_validate.c b/src/mesa/main/api_validate.c
> index a490189..e82e89a 100644
> --- a/src/mesa/main/api_validate.c
> +++ b/src/mesa/main/api_validate.c
> @@ -710,6 +710,19 @@ valid_draw_indirect(struct gl_context *ctx,
>        return GL_FALSE;
>     }
>  
> +   /* From OpenGL ES 3.1 spec. section 10.5:
> +    *     "An INVALID_OPERATION error is generated if zero is bound to
> +    *     VERTEX_ARRAY_BINDING, DRAW_INDIRECT_BUFFER or to any enabled
> +    *     vertex array."
> +    *
> +    * Here we check that vertex buffer bindings match with enabled
> +    * vertex arrays.
> +    */
> +   if (ctx->Array.VAO->_Enabled != ctx->Array.VAO->VertexBindingMask) {
> +      _mesa_error(ctx, GL_INVALID_OPERATION, "%s(No VBO bound)", name);
> +      return GL_FALSE;
> +   }
> +
>     if (!_mesa_valid_prim_mode(ctx, mode, name))
>        return GL_FALSE;
>  
> diff --git a/src/mesa/main/mtypes.h b/src/mesa/main/mtypes.h
> index 4efdf1e..6c6187f 100644
> --- a/src/mesa/main/mtypes.h
> +++ b/src/mesa/main/mtypes.h
> @@ -1419,6 +1419,9 @@ struct gl_vertex_array_object
>     /** Vertex buffer bindings */
>     struct gl_vertex_buffer_binding VertexBinding[VERT_ATTRIB_MAX];
>  
> +   /** Mask indicating which binding points are set. */
> +   GLbitfield64 VertexBindingMask;
> +
>     /** Mask of VERT_BIT_* values indicating which arrays are enabled */
>     GLbitfield64 _Enabled;
>  
> diff --git a/src/mesa/main/varray.c b/src/mesa/main/varray.c
> index 887d0c0..e24342a 100644
> --- a/src/mesa/main/varray.c
> +++ b/src/mesa/main/varray.c
> @@ -174,6 +174,11 @@ bind_vertex_buffer(struct gl_context *ctx,
>        binding->Offset = offset;
>        binding->Stride = stride;
>  
> +      if (vbo == ctx->Shared->NullBufferObj)
> +         vao->VertexBindingMask &= ~VERT_BIT(index);
> +      else
> +         vao->VertexBindingMask |= VERT_BIT(index);
> +
>        vao->NewArrays |= binding->_BoundArrays;
>     }
>  }
> @@ -2126,6 +2131,8 @@ vertex_array_attrib_binding(struct gl_context *ctx,
>  
>     assert(VERT_ATTRIB_GENERIC(attribIndex) < ARRAY_SIZE(vao->VertexAttrib));
>  
> +   vao->VertexBindingMask |= VERT_BIT_GENERIC(attribIndex);

So there are still a few problems here.  The _Enabled bitfield is a mask
of vertex arrays, while VertexBindingMask is a mask of vertex buffer
binding points.  There is no fixed coupling between these states, so the
two bitfields can't be compared.  Yet valid_draw_indirect() compares them.

bind_vertex_buffer() treats VertexBindingMask as a mask of vertex
buffer bindings, while vertex_array_attrib_binding() treats it as a mask
of vertex arrays.  The latter function also incorrectly assumes that if
the association between an vertex attribute and a buffer binding point is
changed, then the new binding point has a vertex buffer set.

I suggest making VertexBindingMask a mask of vertex arrays instead,
so it can be compared with _Enabled, and renaming it to
VertexAttribBufferMask or something similar.  bind_vertex_buffer()
then needs to be changed to set or clear the _BoundArrays bits in the
mask instead of the index bit.  vertex_array_attrib_binding() also
needs to check if the new binding has a buffer set, and update the
attribIndex bit in the mask accordingly.

>     vertex_attrib_binding(ctx, vao,
>                           VERT_ATTRIB_GENERIC(attribIndex),
>                           VERT_ATTRIB_GENERIC(bindingIndex));
>