[Mesa-dev] [PATCH] svga: do primitive trimming in translate_indices()

[Brian Paul]

The index translation code expects the number of indexes to be
consistent with the primitive type (ex: a multiple of 3 for
PIPE_PRIM_TRIANGLES).  If it's not, we can write out of bounds
in the destination buffer.

Fixes failed assertions in the pipebuffer debug code found with
Piglit primitive-restart-draw-mode test.
---
 src/gallium/drivers/svga/svga_draw_elements.c |   15 ++++++++++++---
 1 file changed, 12 insertions(+), 3 deletions(-)

diff --git a/src/gallium/drivers/svga/svga_draw_elements.c b/src/gallium/drivers/svga/svga_draw_elements.c
index fb5f1c9..f6603be 100644
--- a/src/gallium/drivers/svga/svga_draw_elements.c
+++ b/src/gallium/drivers/svga/svga_draw_elements.c
@@ -24,6 +24,7 @@
  **********************************************************/
 
 #include "util/u_inlines.h"
+#include "util/u_prim.h"
 #include "indices/u_indices.h"
 
 #include "svga_cmd.h"
@@ -37,17 +38,25 @@
 
 static enum pipe_error
 translate_indices(struct svga_hwtnl *hwtnl, struct pipe_resource *src,
-                  unsigned offset, unsigned nr, unsigned index_size,
+                  unsigned offset, unsigned prim, unsigned nr,
+                  unsigned index_size,
                   u_translate_func translate, struct pipe_resource **out_buf)
 {
    struct pipe_context *pipe = &hwtnl->svga->pipe;
    struct pipe_transfer *src_transfer = NULL;
    struct pipe_transfer *dst_transfer = NULL;
-   unsigned size = index_size * nr;
+   unsigned size;
    const void *src_map = NULL;
    struct pipe_resource *dst = NULL;
    void *dst_map = NULL;
 
+   /* Need to trim vertex count to make sure we don't write too much data
+    * to the dst buffer in the translate() call.
+    */
+   u_trim_pipe_prim(prim, &nr);
+
+   size = index_size * nr;
+
    dst = pipe_buffer_create(pipe->screen,
                             PIPE_BIND_INDEX_BUFFER, PIPE_USAGE_STATIC, size);
    if (dst == NULL)
@@ -180,7 +189,7 @@ svga_hwtnl_draw_range_elements(struct svga_hwtnl *hwtnl,
       ret = translate_indices(hwtnl,
                               index_buffer,
                               start * index_size,
-                              gen_nr, gen_size, gen_func, &gen_buf);
+                              gen_prim, gen_nr, gen_size, gen_func, &gen_buf);
       if (ret != PIPE_OK)
          goto done;
 
-- 
1.7.10.4