mesa: Delete VAO _MaxElement code and index buffer bounds checking.

Fredrik's implementation of ARB_vertex_attrib_binding introduced new
gl_vertex_attrib_array and gl_vertex_buffer_binding structures, and
converted Mesa's older gl_client_array to be derived state.  Ultimately,
we'd like to drop gl_client_array and use those structures directly.

One hitch is that gl_client_array::_MaxElement doesn't correspond to
either structure (unlike every other field), so we'd have to figure out
where to store it.  The _MaxElement computation uses values from both
structures, so it doesn't really belong in either place.  We could put
it in the VAO, but we'd have to pass it around everywhere.

It turns out that it's only used when ctx->Const.CheckArrayBounds is
set, which is only set by the (rarely used) classic swrast driver.
It appears that drivers/x11 used to set it as well, which was intended
to avoid segmentation faults on out-of-bounds memory access in the X
server (probably for indirect GLX clients).  However, ajax deleted that
code in 2010 (commit 1ccef926be46dce3b6b5c76e812e2fae4e205ce7).

The bounds checking apparently doesn't actually work, either.  Non-VBO
attributes arbitrarily set _MaxElement to 2 * 1000 * 1000 * 1000.
vbo_save_draw and vbo_exec_draw remark /* ??? */ when setting it, and
the i965 code contains a comment noting that _MaxElement is often bogus.

Given that the code is complex, rarely used, and dubiously functional,
it doesn't seem worth maintaining going forward.  This patch drops it.

This will probably mean the classic swrast driver may begin crashing on
out of bounds vertex buffer access in some cases, but I believe that is
allowed by OpenGL (and probably happened for non-VBO accesses anyway).
There do not appear to be any Piglit regressions, either.

Signed-off-by: Kenneth Graunke <[email protected]>
Reviewed-by: Brian Paul <[email protected]>
Reviewed-by: Eric Anholt <[email protected]>
Acked-by: Roland Scheidegger <[email protected]>

9 files changed, 2 insertions, 175 deletions

diff --git a/src/mesa/main/api_validate.c b/src/mesa/main/api_validate.c
index 8f0b1998dad..51a3d1f01ce 100644
--- a/src/mesa/main/api_validate.c
+++ b/src/mesa/main/api_validate.c
@@ -160,47 +160,6 @@ check_valid_to_render(struct gl_context *ctx, const char *function)
 
 
 /**
- * Do bounds checking on array element indexes.  Check that the vertices
- * pointed to by the indices don't lie outside buffer object bounds.
- * \return GL_TRUE if OK, GL_FALSE if any indexed vertex goes is out of bounds
- */
-static GLboolean
-check_index_bounds(struct gl_context *ctx, GLsizei count, GLenum type,
-		   const GLvoid *indices, GLint basevertex)
-{
-   struct _mesa_prim prim;
-   struct _mesa_index_buffer ib;
-   GLuint min, max;
-
-   /* Only the X Server needs to do this -- otherwise, accessing outside
-    * array/BO bounds allows application termination.
-    */
-   if (!ctx->Const.CheckArrayBounds)
-      return GL_TRUE;
-
-   memset(&prim, 0, sizeof(prim));
-   prim.count = count;
-
-   memset(&ib, 0, sizeof(ib));
-   ib.type = type;
-   ib.ptr = indices;
-   ib.obj = ctx->Array.VAO->IndexBufferObj;
-
-   vbo_get_minmax_indices(ctx, &prim, &ib, &min, &max, 1);
-
-   if ((int)(min + basevertex) < 0 ||
-       max + basevertex >= ctx->Array.VAO->_MaxElement) {
-      /* the max element is out of bounds of one or more enabled arrays */
-      _mesa_warning(ctx, "glDrawElements() index=%u is out of bounds (max=%u)",
-                    max, ctx->Array.VAO->_MaxElement);
-      return GL_FALSE;
-   }
-
-   return GL_TRUE;
-}
-
-
-/**
  * Is 'mode' a valid value for glBegin(), glDrawArrays(), glDrawElements(),
  * etc?  The set of legal values depends on whether geometry shaders/programs
  * are supported.
@@ -453,9 +412,6 @@ _mesa_validate_DrawElements(struct gl_context *ctx,
          return GL_FALSE;
    }
 
-   if (!check_index_bounds(ctx, count, type, indices, basevertex))
-      return GL_FALSE;
-
    if (count == 0)
       return GL_FALSE;
 
@@ -517,12 +473,6 @@ _mesa_validate_MultiDrawElements(struct gl_context *ctx,
       }
    }
 
-   for (i = 0; i < primcount; i++) {
-      if (!check_index_bounds(ctx, count[i], type, indices[i],
-                              basevertex ? basevertex[i] : 0))
-         return GL_FALSE;
-   }
-
    return GL_TRUE;
 }
 
@@ -588,9 +538,6 @@ _mesa_validate_DrawRangeElements(struct gl_context *ctx, GLenum mode,
          return GL_FALSE;
    }
 
-   if (!check_index_bounds(ctx, count, type, indices, basevertex))
-      return GL_FALSE;
-
    if (count == 0)
       return GL_FALSE;
 
@@ -623,11 +570,6 @@ _mesa_validate_DrawArrays(struct gl_context *ctx,
    if (!check_valid_to_render(ctx, "glDrawArrays"))
       return GL_FALSE;
 
-   if (ctx->Const.CheckArrayBounds) {
-      if (start + count > (GLint) ctx->Array.VAO->_MaxElement)
-         return GL_FALSE;
-   }
-
    /* From the GLES3 specification, section 2.14.2 (Transform Feedback
     * Primitive Capture):
     *
@@ -692,11 +634,6 @@ _mesa_validate_DrawArraysInstanced(struct gl_context *ctx, GLenum mode, GLint fi
    if (!check_valid_to_render(ctx, "glDrawArraysInstanced(invalid to render)"))
       return GL_FALSE;
 
-   if (ctx->Const.CheckArrayBounds) {
-      if (first + count > (GLint) ctx->Array.VAO->_MaxElement)
-         return GL_FALSE;
-   }
-
    /* From the GLES3 specification, section 2.14.2 (Transform Feedback
     * Primitive Capture):
     *
@@ -791,9 +728,6 @@ _mesa_validate_DrawElementsInstanced(struct gl_context *ctx,
    if (count == 0)
       return GL_FALSE;
 
-   if (!check_index_bounds(ctx, count, type, indices, basevertex))
-      return GL_FALSE;
-
    return GL_TRUE;
 }
 
diff --git a/src/mesa/main/arrayobj.c b/src/mesa/main/arrayobj.c
index 1ea319a746e..0d77b112b31 100644
--- a/src/mesa/main/arrayobj.c
+++ b/src/mesa/main/arrayobj.c
@@ -291,52 +291,6 @@ remove_array_object( struct gl_context *ctx, struct gl_vertex_array_object *obj
 }
 
 
-
-/**
- * Helper for _mesa_update_vao_max_element().
- * \return  min(vao->_VertexAttrib[*]._MaxElement).
- */
-static GLuint
-compute_max_element(struct gl_vertex_array_object *vao, GLbitfield64 enabled)
-{
-   GLuint min = ~((GLuint)0);
-
-   while (enabled) {
-      struct gl_client_array *client_array;
-      GLint attrib = ffsll(enabled) - 1;
-      enabled ^= BITFIELD64_BIT(attrib);
-
-      client_array = &vao->_VertexAttrib[attrib];
-      assert(client_array->Enabled);
-      _mesa_update_array_max_element(client_array);
-      min = MIN2(min, client_array->_MaxElement);
-   }
-
-   return min;
-}
-
-
-/**
- * Examine vertex arrays to update the gl_vertex_array_object::_MaxElement field.
- */
-void
-_mesa_update_vao_max_element(struct gl_context *ctx,
-                                      struct gl_vertex_array_object *vao)
-{
-   GLbitfield64 enabled;
-
-   if (!ctx->VertexProgram._Current ||
-       ctx->VertexProgram._Current == ctx->VertexProgram._TnlProgram) {
-      enabled = _mesa_array_object_get_enabled_ff(vao);
-   } else {
-      enabled = _mesa_array_object_get_enabled_arb(vao);
-   }
-
-   /* _MaxElement is one past the last legal array element */
-   vao->_MaxElement = compute_max_element(vao, enabled);
-}
-
-
 /**
  * Updates the derived gl_client_arrays when a gl_vertex_attrib_array
  * or a gl_vertex_buffer_binding has changed.
diff --git a/src/mesa/main/arrayobj.h b/src/mesa/main/arrayobj.h
index d72761db15f..1819cd12a2b 100644
--- a/src/mesa/main/arrayobj.h
+++ b/src/mesa/main/arrayobj.h
@@ -75,10 +75,6 @@ _mesa_initialize_vao(struct gl_context *ctx,
 
 
 extern void
-_mesa_update_vao_max_element(struct gl_context *ctx,
-                             struct gl_vertex_array_object *vao);
-
-extern void
 _mesa_update_vao_client_arrays(struct gl_context *ctx,
                                struct gl_vertex_array_object *vao);
 
diff --git a/src/mesa/main/attrib.c b/src/mesa/main/attrib.c
index 2e289b6f1cb..ef98ba7fd39 100644
--- a/src/mesa/main/attrib.c
+++ b/src/mesa/main/attrib.c
@@ -1458,7 +1458,6 @@ copy_array_object(struct gl_context *ctx,
    /* _Enabled must be the same than on push */
    dest->_Enabled = src->_Enabled;
    dest->NewArrays = src->NewArrays;
-   dest->_MaxElement = src->_MaxElement;
 }
 
 /**
diff --git a/src/mesa/main/context.c b/src/mesa/main/context.c
index 4c2c32e7b7a..682b9c79718 100644
--- a/src/mesa/main/context.c
+++ b/src/mesa/main/context.c
@@ -628,9 +628,6 @@ _mesa_init_constants(struct gl_constants *consts, gl_api api)
     */
    consts->VertexID_is_zero_based = false;
 
-   /* CheckArrayBounds is overriden by drivers/x11 for X server */
-   consts->CheckArrayBounds = GL_FALSE;
-
    /* GL_ARB_draw_buffers */
    consts->MaxDrawBuffers = MAX_DRAW_BUFFERS;
 
diff --git a/src/mesa/main/mtypes.h b/src/mesa/main/mtypes.h
index 0d50be842fb..553a216672a 100644
--- a/src/mesa/main/mtypes.h
+++ b/src/mesa/main/mtypes.h
@@ -1526,7 +1526,6 @@ struct gl_client_array
    GLuint _ElementSize;         /**< size of each element in bytes */
 
    struct gl_buffer_object *BufferObj;/**< GL_ARB_vertex_buffer_object */
-   GLuint _MaxElement;          /**< max element index into array buffer + 1 */
 };
 
 
@@ -1629,12 +1628,6 @@ struct gl_vertex_array_object
    /** Mask of VERT_BIT_* values indicating changed/dirty arrays */
    GLbitfield64 NewArrays;
 
-   /**
-    * Min of all enabled arrays' _MaxElement.  When arrays reside inside VBOs
-    * we can determine the max legal (in bounds) glDrawElements array index.
-    */
-   GLuint _MaxElement;
-
    /** The index buffer (also known as the element array buffer in OpenGL). */
    struct gl_buffer_object *IndexBufferObj;
 };
@@ -3432,9 +3425,6 @@ struct gl_constants
       GLuint PrimitivesWritten;
    } QueryCounterBits;
 
-   /** vertex array / buffer object bounds checking */
-   GLboolean CheckArrayBounds;
-
    GLuint MaxDrawBuffers;    /**< GL_ARB_draw_buffers */
 
    GLuint MaxColorAttachments;   /**< GL_EXT_framebuffer_object */
diff --git a/src/mesa/main/state.c b/src/mesa/main/state.c
index c122c16aae3..80287c47062 100644
--- a/src/mesa/main/state.c
+++ b/src/mesa/main/state.c
@@ -419,11 +419,6 @@ _mesa_update_state_locked( struct gl_context *ctx )
    if (new_state & _NEW_ARRAY)
       _mesa_update_vao_client_arrays(ctx, ctx->Array.VAO);
 
-   if (ctx->Const.CheckArrayBounds &&
-       new_state & (_NEW_ARRAY | _NEW_PROGRAM | _NEW_BUFFER_OBJECT)) {
-      _mesa_update_vao_max_element(ctx, ctx->Array.VAO);
-   }
-
  out:
    new_prog_state |= update_program_constants(ctx);
 
diff --git a/src/mesa/main/varray.c b/src/mesa/main/varray.c
index 7d169f9d49b..ead78649db8 100644
--- a/src/mesa/main/varray.c
+++ b/src/mesa/main/varray.c
@@ -1867,7 +1867,6 @@ _mesa_copy_client_array(struct gl_context *ctx,
    dst->InstanceDivisor = src->InstanceDivisor;
    dst->_ElementSize = src->_ElementSize;
    _mesa_reference_buffer_object(ctx, &dst->BufferObj, src->BufferObj);
-   dst->_MaxElement = src->_MaxElement;
 }
 
 void
@@ -1911,11 +1910,10 @@ print_array(const char *name, GLint index, const struct gl_client_array *array)
       printf("  %s[%d]: ", name, index);
    else
       printf("  %s: ", name);
-   printf("Ptr=%p, Type=0x%x, Size=%d, ElemSize=%u, Stride=%d, Buffer=%u(Size %lu), MaxElem=%u\n",
+   printf("Ptr=%p, Type=0x%x, Size=%d, ElemSize=%u, Stride=%d, Buffer=%u(Size %lu)\n",
 	  array->Ptr, array->Type, array->Size,
 	  array->_ElementSize, array->StrideB,
-	  array->BufferObj->Name, (unsigned long) array->BufferObj->Size,
-	  array->_MaxElement);
+	  array->BufferObj->Name, (unsigned long) array->BufferObj->Size);
 }
 
 
@@ -1928,8 +1926,6 @@ _mesa_print_arrays(struct gl_context *ctx)
    struct gl_vertex_array_object *vao = ctx->Array.VAO;
    GLuint i;
 
-   _mesa_update_vao_max_element(ctx, vao);
-
    printf("Array Object %u\n", vao->Name);
    if (vao->_VertexAttrib[VERT_ATTRIB_POS].Enabled)
       print_array("Vertex", -1, &vao->_VertexAttrib[VERT_ATTRIB_POS]);
@@ -1943,7 +1939,6 @@ _mesa_print_arrays(struct gl_context *ctx)
    for (i = 0; i < VERT_ATTRIB_GENERIC_MAX; i++)
       if (vao->_VertexAttrib[VERT_ATTRIB_GENERIC(i)].Enabled)
          print_array("Attrib", i, &vao->_VertexAttrib[VERT_ATTRIB_GENERIC(i)]);
-   printf("  _MaxElement = %u\n", vao->_MaxElement);
 }
 
 
diff --git a/src/mesa/main/varray.h b/src/mesa/main/varray.h
index d5d8b363d43..4e4bd5f80a7 100644
--- a/src/mesa/main/varray.h
+++ b/src/mesa/main/varray.h
@@ -34,39 +34,6 @@
 struct gl_client_array;
 struct gl_context;
 
-
-/**
- * Compute the index of the last array element that can be safely accessed in
- * a vertex array.  We can really only do this when the array lives in a VBO.
- * The array->_MaxElement field will be updated.
- * Later in glDrawArrays/Elements/etc we can do some bounds checking.
- */
-static inline void
-_mesa_update_array_max_element(struct gl_client_array *array)
-{
-   assert(array->Enabled);
-
-   if (array->BufferObj->Name) {
-      GLsizeiptrARB offset = (GLsizeiptrARB) array->Ptr;
-      GLsizeiptrARB bufSize = (GLsizeiptrARB) array->BufferObj->Size;
-
-      if (offset < bufSize) {
-         const GLuint stride = array->StrideB ?
-                                 array->StrideB : array->_ElementSize;
-         array->_MaxElement = (bufSize - offset + stride
-                                  - array->_ElementSize) / stride;
-      }
-      else {
-	 array->_MaxElement = 0;
-      }
-   }
-   else {
-      /* user-space array, no idea how big it is */
-      array->_MaxElement = 2 * 1000 * 1000 * 1000; /* just a big number */
-   }
-}
-
-
 /**
  * Returns a pointer to the vertex attribute data in a client array,
  * or the offset into the vertex buffer for an array that resides in